For now, because you haven't published the module yet, you need to adapt the example.com/hello module so it can find the example.com/greetings code on your local file system.

模块感知模式

use the go mod edit command to edit the example.com/hello module to redirect Go tools from its module path (where the module isn't) to the local directory (where it is).

go mod edit -replace example.com/greetings=../greetings