helloworld.go:2:8: cannot find package "fmt" in any of:

[lizitong67]

I encountered the following error in ubuntu18 and manjaro, why?

Setting up environment...

I will now run a test Hello World program with Go to ensure things are OK...
helloworld.go:2:8: cannot find package "fmt" in any of:
        /home/gosint/go/src/fmt (from $GOROOT)
        /home/gosint/projects/src/fmt (from $GOPATH)
package main
        imports runtime: cannot find package "runtime" in any of:
        /home/gosint/go/src/runtime (from $GOROOT)
        /home/gosint/projects/src/runtime (from $GOPATH)
Some error encountered...