Packages & Modules

Go packages & modules. Best practices. How to organise things. How to use new shiny modules.

Transcript

1. Packages & Modules Oleg Kovalov
2. Agenda
3. In this talk 3 - About me - Packages - Modules - Summary - Q&A
4. In this talk + extra 4 - About me - Packages - Modules - Summary - Q&A Interfaces
5. About me
6. I don’t have a Soundcloud... 6
7. - Gopher for ~4 years I don’t have a Soundcloud...but 7
8. I don’t have a Soundcloud...but 8 - Gopher for ~4 years - Open-source contributor - Go-critic - static analysis tool - Go-advice - list of Go tips @ GoGoConf 2018
9. I don’t have a Soundcloud...but 9 - Gopher for ~4 years - Open-source contributor - Go-critic - static analysis tool - Go-advice - list of Go tips @ GoGoConf 2018 - Engineer at allegro.pl core team
10. - Gopher for ~4 years - Open-source contributor - Go-critic - static analysis tool - Go-advice - list of Go tips @ GoGoConf 2018 - Engineer at allegro.pl core team Website: https://olegk.dev Twitter: @oleg_kovalov Github: @cristaloleg I don’t have a Soundcloud...but 10 Twitter & slides
11. Packages
12. Naming 12
13. - Short and clear Naming 13
14. - Short and clear - May be abbreviated when the abbreviation is familiar Naming 14
15. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand Naming 15
16. Naming - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand See standard packages for good examples - io (input and output) 16
17. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand See standard packages for good examples - io (input and output) - strconv (string conversion) Naming 17
18. - Short and clear - May be abbreviated when the abbreviation is familiar - Abbrv name is easy to understand See standard packages for good examples - io (input and output) - strconv (string conversion) - syscall (system call) Naming 18
19. Naming don’ts 19
20. - If abbreviating is unclear Naming don’ts 20
21. - If abbreviating is unclear - If name is ambiguous Naming don’ts 21
22. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase Naming don’ts 22
23. Naming don’ts - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase - psdb (Postgres? Parallel search?) 23
24. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase - psdb (Postgres? Parallel search?) - srv (service? server? surviving?) Naming don’ts 24
25. - If abbreviating is unclear - If name is ambiguous - snake_case or camelCase - psdb (Postgres? Parallel search?) - srv (service? server? surviving?) - buf (buffer? buffer what? WoW buff?) Naming don’ts 25
26. - Avoid giving a package a name that is commonly used in client code Don’t steal good names 26
27. - Avoid giving a package a name that is commonly used in client code - buf is a good variable name for a buffer - the buffered I/O package is called bufio (buffer + io) Don’t steal good names 27
28. - Avoid giving a package a name that is commonly used in client code - buf is a good variable name for a buffer - the buffered I/O package is called bufio (buffer + io) - client is a good name for...client - but not a package name Don’t steal good names 28
29. - Avoid giving a package a name that is commonly used in client code - buf is a good variable name for a buffer - the buffered I/O package is called bufio (buffer + io) - client is a good name for...client - but not a package name - imagine a replacement for it Don’t steal good names 29 c ? clnt ? cli ? clientHTTP ?
30. ...and few from std packages 30
31. These std packages are a good names thiefs: - path - path/filepath - net/url And you cannot use your variable url easily, oh :( ...and few from std packages 31
32. ...and few from std packages 32 These std packages are a good names thiefs: - path - path/filepath - net/url And you cannot use your variable url easily, oh :( But there are good examples: - strings - bytes - net/urls instead of net/url looks good enough
33. Most of the projects in Go are flat and this is fine Try to keep clean import paths 33
34. Most of the projects in Go are flat and this is fine - Try to keep it clean github.com/foo/bar/pl/goava/src/main/code/go/validation Try to keep clean import paths 34
35. Most of the projects in Go are flat and this is fine - Try to keep it clean github.com/foo/bar/pl/goava/src/main/code/go/validation - Avoid do src/ or pkg/ (in most cases) gitlab.com/foo/bar/pkg/process Try to keep clean import paths 35
36. Write shy code - modules that don’t reveal anything unnecessary to other modules and that don’t rely on other modules' implementations. --- Dave Thomas (with Andy Hunt, he co-authored The Pragmatic Programmer) Shy packages 36
37. Write shy code - modules that don’t reveal anything unnecessary to other modules and that don’t rely on other modules' implementations. --- Dave Thomas (with Andy Hunt, he co-authored The Pragmatic Programmer) And shy also means: 1 package = 1 thing Shy packages 37
38. Let’s put all structs into model(s) package 38
39. Nice 39
40. Yeah! 40
41. Oh wait... 41
42. ... 42
43. PLZ STAHP 43
44. Models package is a weak idea 44
45. - Organize by functional responsibility Models package is a weak idea, so 45
46. - Organize by functional responsibility - Don’t put all the type into models package Models package is a weak idea, so 46
47. Models package is a weak idea, so 47 - Organize by functional responsibility - Don’t put all the type into models package - Keeping them in one gives nothing
48. Models package is a weak idea, so 48 - Organize by functional responsibility - Don’t put all the type into models package - Keeping them in one gives nothing - In the end this will be a spaghetti code
49. Models package is a weak idea, so 49 - Organize by functional responsibility - Don’t put all the type into models package - Keeping them in one gives nothing - In the end this will be a spaghetti code - (The same applies to the interfaces, implementations and so on)
50. One of the possible structures 50 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
51. One of the possible structures 51 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
52. One of the possible structures 52 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
53. One of the possible structures 53 mock.NewBlog(...) . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
54. One of the possible structures 54 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
55. One of the possible structures 55 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
56. One of the possible structures 56 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
57. pkg, internal, misc or util Whatever works for your team and you One of the possible structures 57 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
58. One of the possible structures 58 . ├── app ├── cmd │ └── <project-name> ├── blog ├── comment ├── mock ├── pkg │ ├── superpay │ └── validation ├── store │ └── postgres ├── user └── <project-name>.go
59. Avoid util/common/base/helpers packages 59
60. - util.URLError Avoid util/common/base/helpers packages 60
61. - util.URLError - common.SanitizeMessage Avoid util/common/base/helpers packages 61
62. - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath Avoid util/common/base/helpers packages 62
63. - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail Avoid util/common/base/helpers packages 63
64. - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail Avoid util/common/base/helpers packages 64 These packages say nothing!
65. Avoid util/common/base/helpers packages 65 - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail type URLError = app.URLError These packages say nothing!
66. Avoid util/common/base/helpers packages 66 - util.URLError - common.SanitizeMessage - base.EnsureAbsolutePath - helpers.IsEmail type URLError = app.URLError var isEmail = validation.IsEmail These packages say nothing!
67. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go Inside the package 67
68. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go // type Comment and Comment.HasImage method Inside the package 68
69. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go // type User and type Credentials │ └── user_test.go └── redis ├── redis.go └── comments.go Inside the package 69
70. - Use multiple files - Do not separate structs and their methods (not a C/C++) - It’s okay to store few structs in one file (it’s not Java after all) - And keep test files next to code store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go Inside the package 70
71. Is this storage? Stats? Cache? Benchmark suites? 71 postgres ├── postgres.go ├── user.go ├── stats.go └── user_test.go redis ├── redis.go ├── cache.go └── comments.go
72. Is this storage? Stats? Cache? Benchmark suites? 72 postgres ├── postgres.go ├── user.go ├── stats.go └── user_test.go redis ├── redis.go ├── cache.go └── comments.go cache ├── redis │ └── redis.go store ├── postgres │ ├── postgres.go │ ├── user.go │ └── user_test.go └── redis ├── redis.go └── comments.go
73. What about main package? 73
74. - Main packages are not importable What about main package? 74
75. - Main packages are not importable - Don’t export from main, it’s useless What about main package? 75
76. - Main packages are not importable - Don’t export from main, it’s useless - main package is hard to test (see above) What about main package? 76
77. Keep your main simple and testable 77 package main func init() { config.Load() }
78. Keep your main simple and testable 78 package main func init() { config.Load() } func main() { os.Exit(realMain()) } func realMain() int { log.SetOutput(ioutil.Discard) // ... }
79. package main func main() { log.Fatal(app.Run()) } Keep your main simpler 79
80. Keep your init() light 80
81. - 1 init() per package (pretty please) Keep your init() light 81
82. - 1 init() per package (pretty please) - Do not depend on init’s call order Keep your init() light 82
83. - 1 init() per package (pretty please) - Do not depend on init’s call order - No heavy tasks Keep your init() light 83
84. - 1 init() per package (pretty please) - Do not depend on init’s call order - No heavy tasks - Preferably no I/O, especially blocking Keep your init() light 84
85. - 1 init() per package (pretty please) - Do not depend on init’s call order - No heavy tasks - Preferably no I/O, especially blocking - Better to not have it at all Keep your init() light 85
86. # Python is quite flexible # try: import foo except: print(‘good try lol’) panic in init() 86
87. # Python is quite flexible # try: import foo except: print(‘good try lol’) // Go isn’t so… // package foo func init() { iCanPanicAndYouCanDoNothing() } panic in init() 87
88. // but wait, it can be flexible... package foo func Init() { iCanPanicButOoooohhYouCanCatchMe() } panic in init() 88
89. panic in init() // but wait, it can be flexible... package foo func Init() { iCanPanicButOoooohhYouCanCatchMe() } ----------- package bar func ... { defer func() { if r := recover(); r != nil { // process a panic } }() foo.Init() } 89
90. package foo func (s *Service) Process() { // let’s start a sweet goroutine go func() { iCanPanicAndYouCanDoNothing() }() } I heard you like goroutines 90
91. package foo func (s *Service) Process() { // let’s start a sweet goroutine go func() { iCanPanicAndYouCanDoNothing() }() } ----------- package bar func ... { // but internal goroutine // isn’t accessible here :( s.Process() } I heard you like goroutines 91
92. package foo func (s *Service) Process() { go func() { defer func() { // recovery process }() iCanPanicAndAuthorWillRecover() }() } I heard you like goroutines 92
93. package foo func (s *Service) Process() { iCanPanicButItDoesntMatter() } I heard you like goroutines 93
94. package foo func (s *Service) Process() { iCanPanicButItDoesntMatter() } ----------- package bar func ... { go func() { defer func() { // user defined recovery process }() s.Process() }() } I heard you like goroutines 94
95. Global state 95
96. - Exported package variable is mutable by everyone Global state 96
97. - Exported package variable is mutable by everyone - You have no power to control other packages Global state 97
98. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible Global state 98
99. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! Global state 99
100. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe Global state 100
101. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe - Config, flags? - better no Global state 101
102. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe - Config, flags? - better no - DB driver? - NONONO Global state 102
103. - Exported package variable is mutable by everyone - You have no power to control other packages - Tight coupling makes code less flexible - You cannot mock a package! - Logger, metrics? - mmmmaybe - Config, flags? - better no - DB driver? - NONONO Global state 103 by the way unexported variables are also bad :(
104. Good package == stateless container 104
105. - Should be simply a container for consts, types, funcs Good package == stateless container 105
106. - Should be simply a container for consts, types, funcs - Zero variables is brilliant (both exported and unexported) Good package == stateless container 106
107. - Should be simply a container for consts, types, funcs - Zero variables is brilliant (both exported and unexported) - Documentation and tests :) Good package == stateless container 107
108. Logging is cool 108
109. - log.Printf A safe action, might be noisy, but harmless Logging is cool, but... 109
110. - log.Printf A safe action, might be noisy, but harmless - log.Panicf Not idiomatic, but in an edge case might be fine Logging is cool, but... 110
111. Logging is cool, but... 111 - log.Printf A safe action, might be noisy, but harmless - log.Panicf Not idiomatic, but in an edge case might be fine - log.Fatalf Evil has no boundaries, omit it, no one can survive os.Exit(1) (even defer)
112. Forgotten doc.go 112
113. - doc.go is a README of your package Forgotten doc.go 113
114. - doc.go is a README of your package - Run godoc locally to see how it looks Forgotten doc.go 114
115. Forgotten doc.go 115 - doc.go is a README of your package - Run godoc locally to see how it looks - Also add package documentation // Package bytes implements functions for the manipulation of byte slices. // It is analogous to the facilities of the strings package. package bytes
116. Interfaces
117. Accept interfaces, return structs 117
118. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia Accept interfaces, return structs 118
119. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia TCP architecture: Accept interfaces, return structs 119
120. Accept interfaces, return structs Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia TCP architecture: - We don’t care about how packets go through network 120
121. Be conservative in what you send, be liberal in what you accept (с) Postel’s Law, Wikipedia TCP architecture: - We don’t care about how packets go through network - but we expect them in a well defined order to process Accept interfaces, return structs 121
122. func FetchUsers(db Store) ([]*User, error) { ... } Accept interfaces, return structs 122
123. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock Accept interfaces, return structs 123
124. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock - Until it has desired API for us Accept interfaces, return structs 124
125. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock - Until it has desired API for us - But we know for sure that we need a specific struct User Accept interfaces, return structs 125
126. func FetchUsers(db Store) ([]*User, error) { ... } - We don’t care what is inside: Postgres, Redis, plain file or a mock - Until it has desired API for us - But we know for sure that we need a specific struct User Tip: return error as interface, not as a struct Accept interfaces, return structs 126
127. Where to declare interfaces? 127
128. - There is the “Java-style” interface declaration Where to declare interfaces? 128
129. - There is the “Java-style” interface declaration - Define an interface Where to declare interfaces? 129
130. - There is the “Java-style” interface declaration - Define an interface - Create a type that implements it Where to declare interfaces? 130
131. Where to declare interfaces? 131 - There is the “Java-style” interface declaration - Define an interface - Create a type that implements it - Often you have one interface and one implementation
132. Where to declare interfaces? - There is the “Java-style” interface declaration - Define an interface - Create a type that implements it - Often you have one interface and one implementation That’s not a “Go style” ʕ◔ϖ◔ʔ 132
133. Where to declare Go interfaces? 133
134. - Go interfaces are in the package that uses it Where to declare Go interfaces? 134
135. - Go interfaces are in the package that uses it - And this makes Go code easy to extend Where to declare Go interfaces? 135
136. Modules
137. Long story short time 137 time Image credit: ©Istockphoto/JamesBrey
138. Pre-modules era 138
139. - GOPATH Pre-modules era (2012-...) Go 1.0 139
140. - GOPATH - godep Pre-modules era (2013-...) 140
141. - GOPATH - godep - gopkg.in Pre-modules era (2014-...) 141
142. - GOPATH - godep - gopkg.in - glide Pre-modules era (2014-...) 142
143. - GOPATH - godep - gopkg.in - glide - vendor dir Pre-modules era (2015-...) Go 1.5 143
144. - GOPATH - godep - gopkg.in - glide - vendor dir - dep Pre-modules era (2017-...) 144
145. Go modules (2018) 145
146. Go modules 146 - Modules - Semantic versioning - Import compatibility rule - go.mod
147. - A module is a collection of Go packages that are versioned as a single unit What is a module? 147
148. - A module is a collection of Go packages that are versioned as a single unit - A module is a tree/directory of Go source files with a go.mod file in the root ├── cmd │ └── main.go ├── consum │ ├── consum.go │ └── handlers.go ├── produce │ ├── handlers.go │ ├── handlers_test.go │ └── processing.go ├── go.mod └── go.sum What is a module? 148
149. - A module is a collection of Go packages that are versioned as a single unit - A module is a tree/directory of Go source files with a go.mod file in the root ├── cmd │ └── main.go ├── consum │ ├── consum.go │ └── handlers.go ├── produce │ ├── handlers.go │ ├── handlers_test.go │ └── processing.go ├── go.mod └── go.sum What is a module? 149 Can leave outside of GOPATH
150. Semantic versioning (https://semver.org) 150
151. Import compatibility rule 151 - If an old and a new package have the same import path - the new package must be backwards-compatible with the old package
152. Import compatibility rule 152 - If an old and a new package have the same import path - the new package must be backwards-compatible with the old package import ( "github.com/golang/hello/hey" // v0 or v1 "github.com/golang/hello/v2/hey" )
153. How to enable modules? 153 - auto(default) - on - off $ export GO111MODULE=on $ go build ./...
154. go mod commands 154 Usage: go mod <command> [arguments] The commands are: download download modules to local cache edit edit go.mod from tools or scripts graph print module requirement graph init initialize new module in current directory tidy add missing and remove unused modules vendor make vendored copy of dependencies verify verify dependencies have expected content why explain why packages or modules are needed
155. $ mkdir /mygo/hello $ cd /mygo/hello Let’s start with modules 155
156. Let’s start with modules $ mkdir /mygo/hello $ cd /mygo/hello $ go mod init github.com/golang/hello go: creating new go.mod: module github.com/golang/hello $ ls go.mod 156
157. Let’s start with modules 157 $ mkdir /mygo/hello $ cd /mygo/hello $ go mod init github.com/golang/hello go: creating new go.mod: module github.com/golang/hello $ ls go.mod $ cat go.mod module github.com/golang/hello
158. $ git clone https://github.com/go-gitea/gitea Cloning into gitea... $ cd gitea Convert to modules 158
159. $ git clone https://github.com/go-gitea/gitea Cloning into gitea... $ cd gitea $ go mod init go: creating new go.mod: module github.com/go-gitea/gitea go: copying requirements from Gopkg.lock Convert to modules 159
160. Convert to modules 160 $ git clone https://github.com/go-gitea/gitea Cloning into gitea... $ cd gitea $ go mod init go: creating new go.mod: module github.com/go-gitea/gitea go: copying requirements from Gopkg.lock $ go mod tidy go: extracting github.com/PuerkitoBio/goquery v1.5.0 go: extracting github.com/blevesearch/bleve v0.7.0 go: finding github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57 go: finding golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961 go: finding golang.org/x/time v0.0.0-20181108054448-85acf8d2951c go: downloading github.com/facebookgo/grace v0.0.0-20180706040059-75cf19382434 ...
161. How to read go.mod? module github.com/hashicorp/consul go 1.12 ... 161
162. How to read go.mod? module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) 162
163. module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) How to read go.mod? 163
164. How to read go.mod? 164 module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) replace github.com/hashicorp/consul/api => ./api // can be fork or branch
165. How to read go.mod? 165 module github.com/hashicorp/consul go 1.12 require ( github.com/NYTimes/gziphandler v1.0.1 <...>/datadog-go v0.0.0-20160329135253-cc2f4770f4d6 // indirect github.com/go-redis/redis v6.15.2+incompatible ... ) replace github.com/hashicorp/consul/api => ./api // can be fork or branch exclude github.com/not-a-hacker/supergeil v1270.0.1
166. How to read go.sum? 166
167. How to read go.sum? 167
168. How to read go.sum? 168 cloud.google.com/go v0.26.0 h1:e0WKqKTd5BnrG8aKH3J3h+QvEIQtSUcf2n5UZ5ZgLtQ= cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw= github.com/Azure/azure-sdk-for-go v16.0.0+incompatible h1:gr1qKY/Ll72VjFTZmaBwRK1yQHAxCnV25ekOKroc9ws= github.com/Azure/azure-sdk-for-go v16.0.0+incompatible/go.mod h1:9XXNKU+eRnpl9moKnB4QOLf1HestfXbmab5FXxiDBjc= // you might want to use go mod verify
169. go get understands versioning 169
170. # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest go get understands versioning 170
171. # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest # records v1.6.2 $ go get github.com/gorilla/mux@v1.6.2 $ go get github.com/gorilla/mux@e3702bed2 go get understands versioning 171
172. go get understands versioning # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest # records v1.6.2 $ go get github.com/gorilla/mux@v1.6.2 $ go get github.com/gorilla/mux@e3702bed2 # records v0.0.0-20180517173623-c85619274f5d $ go get github.com/gorilla/mux@c856192 172
173. go get understands versioning 173 # same (@latest is default for 'go get') $ go get github.com/gorilla/mux@latest # records v1.6.2 $ go get github.com/gorilla/mux@v1.6.2 $ go get github.com/gorilla/mux@e3702bed2 # records v0.0.0-20180517173623-c85619274f5d $ go get github.com/gorilla/mux@c856192 # records current meaning of master $ go get github.com/gorilla/mux@master
174. # go and get a repo $ go get github.com/go-gitea/gitea $ cd ~/go/src/github.com/go-gitea/gitea go mod why 174
175. # go and get a repo $ go get github.com/go-gitea/gitea $ cd ~/go/src/github.com/go-gitea/gitea # set a env var and check why do we use this dependency $ export GO111MODULE=on $ go mod why github.com/RoaringBitmap/roaring go mod why 175
176. go mod why 176 # go and get a repo $ go get github.com/go-gitea/gitea $ cd ~/go/src/github.com/go-gitea/gitea # set a env var and check why do we use this dependency $ export GO111MODULE=on $ go mod why github.com/RoaringBitmap/roaring # github.com/RoaringBitmap/roaring code.gitea.io/gitea/modules/indexer github.com/blevesearch/bleve github.com/blevesearch/bleve/index/scorch github.com/RoaringBitmap/roaring
177. # install $ go get github.com/rogpeppe/gohack gohack by Roger Peppe 177
178. # install $ go get github.com/rogpeppe/gohack $ gohack get example.com/foo/bar # will clone repo into $HOME/gohack/example.com/foo/bar # will add replace statement $ cat go.mod replace example.com/foo/bar => /home/rog/gohack/example.com/foo/bar gohack by Roger Peppe 178
179. gohack by Roger Peppe 179 # install $ go get github.com/rogpeppe/gohack $ gohack get example.com/foo/bar # will clone repo into $HOME/gohack/example.com/foo/bar # will add replace statement $ cat go.mod replace example.com/foo/bar => /home/rog/gohack/example.com/foo/bar # to remove specific replace: $ gohack undo example.com/foo/bar # to remove all replaces: $ gohack undo
180. GOPROXY 180
181. GOPROXY 181 - https://proxy.golang.org - https://github.com/gomods/athens - https://github.com/goproxy/goproxy - export GOPROXY=my.proxy.com - go get github.com/foo/bar
182. Why package management is hard? 182
183. *Remark
184. Application != Library 184
185. - Usability ~ Reusability Application != Library 185
186. - Usability ~ Reusability - Make application team-friendly Application != Library 186
187. - Usability ~ Reusability - Make application team-friendly - Keep library easy to use Application != Library 187
188. - Usability ~ Reusability - Make application team-friendly - Keep library easy to use Animated-emoji-colorful output in app - cool, whatever Application != Library 188
189. - Usability ~ Reusability - Make application team-friendly - Keep library easy to use Animated-emoji-colorful output in app - cool, whatever Math library with zero allocation HTTP router - thanks, but no Application != Library 189
190. Summary
191. Summary 191
192. - Simple and shy packages Summary 192
193. - Simple and shy packages - Clear naming is important Summary 193
194. - Simple and shy packages - Clear naming is important - No global state at all Summary 194
195. Summary - Simple and shy packages - Clear naming is important - No global state at all - Interfaces are for abstraction 195
196. Summary 196 - Simple and shy packages - Clear naming is important - No global state at all - Interfaces are for abstraction - Modules == Go ecosystem 2.0
197. Summary 197 - Simple and shy packages - Clear naming is important - No global state at all - Interfaces are for abstraction - Modules == Go ecosystem 2.0 - App != Lib
198. Q&A
199. - Ben Johnson @benbjohnson - Dave Cheney @davecheney - Jaana B. Dogan @rakyll - Go team ʕ◔ϖ◔ʔ - all the friends \o/ Thanks 199
200. Thank You