package main

import (
	"fmt"
	"os"
	"os/exec"
	"plugin"
)

func main() {
	output, err := exec.Command("go", "build", "-buildmode=plugin", "-o=bar.so", "bar.go").CombinedOutput()
	if err != nil {
		fmt.Printf("%s\n", output)
		panic(err)
	}

	p, err := plugin.Open("bar.so")
	if err != nil {
		panic(err)
	}
	f, err := p.Lookup("Fn")
	if err != nil {
		panic(err)
	}
	f.(func())()

	// build bar2.go
	err = os.Remove("bar.so")
	if err != nil {
		panic(err)
	}
	output, err = exec.Command("go", "build", "-buildmode=plugin", "-o=bar.so", "bar2.go").CombinedOutput()
	if err != nil {
		fmt.Printf("%s\n", output)
		panic(err)
	}

	// reload
	p, err = plugin.Open("bar.so")
	if err != nil {
		panic(err)
	}
	f, err = p.Lookup("Fn")
	if err != nil {
		panic(err)
	}
	f.(func())()

}

package main

func Fn() {
	println("bar1")
}

package main

func Fn() {
	println("bar2")
}

go run main.go

bar1
bar2

bar1
bar1

go version devel +120cf67 Fri Nov 18 17:25:07 2016 +0000 linux/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/reus"
GORACE=""
GOROOT="/home/reus/go"
GOTOOLDIR="/home/reus/go/pkg/tool/linux_amd64"
TERM="dumb"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build816756848=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
GOROOT/bin/go version: go version devel +120cf67 Fri Nov 18 17:25:07 2016 +0000 linux/amd64
GOROOT/bin/go tool compile -V: compile version devel +120cf67 Fri Nov 18 17:25:07 2016 +0000 X:framepointer
uname -sr: Linux 4.8.7-1-ARCH
/usr/lib/libc.so.6: GNU C Library (GNU libc) stable release version 2.24, by Roland McGrath et al.
gdb --version: GNU gdb (GDB) 7.12