Add process.Release for unix

Signed-off-by: leongross <leon.gross@9elements.com>

src/os/exec_posix.go

@@ -7,6 +7,7 @@
 package os
 
 import (
+	"runtime"
 	"syscall"
 )
 
@@ -24,3 +25,11 @@ var (
 func findProcess(pid int) (*Process, error) {
 	return &Process{Pid: pid}, nil
 }
+
+func (p *Process) release() error {
+	// NOOP for unix.
+	p.Pid = -1
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(p, nil)
+	return nil
+}