$GOPATH/
   src/
     huru/
       side.go
       hello.go

package main

import (
    "encoding/json"
    "log"
    "net/http"
    "github.com/gorilla/mux"
)

Foo()

package main

func Foo() {

}

go install huru

# huru
src/huru/hello.go:12:1: syntax error: non-declaration statement outside function body