[Go] How to reuse class libraries? How to use the custom package in the project?

1. The package must be placed under the src
2. The package is a folder
3. To use the library in this project, you
need to add the two-level directory addresses of the location of the package to the Project GOPATH
4. Use the library in other projects, you
need to add this Adding the upper two-level directory addresses of the package location to Global GOPATH It is
not recommended to add Global GOPATH
but to throw the package into the default Global GOPATH