The Go compiler can compile the Go source go with different go specs. Fo example, if you have installed go 1.14, you can compile your source with Go spec 1.13.

The rules for which version of the Go spec used during compilation appear to be

1. If your source code is stored within the GOPATH (or you have disabled modules with GO111MODULE=off) then the version of the Go spec used to compile matches the version of the compiler you are using. ie if you have go 1.13(GOROOT points to your go installation) installed then the go spec used will be 1.13
2. If your source code is outside the GOPATH(or GO111MODULE=on), then the go tool will take the version from the go.mod file
3. If no go.mod file is provided, then same as point 1
4. If you are in module mode(see point 2) and no version is specified in the go.mod file, then go 1.13 is used by default

The last point is interesting.

Reference: https://www.jetbrains.com/help/go/configuring-goroot-and-gopath.html