interoperation with older versions of Go, or to ensure that all files used for a build are stored in a single file tree. https://go.dev/ref/mod#vendoring より抜粋
the mirror to continue to serve source code that is no longer available from the original locations. https://go.dev/blog/module-mirror-launch#module-mirror より抜粋
forever. There are a number of reasons for this, but one reason is if proxy.golang.org is not able to detect a suitable license. https://proxy.golang.org/ より抜粋
interoperation with older versions of Go, or to ensure that all files used for a build are stored in a single file tree. https://go.dev/ref/mod#vendoring より抜粋