Add process.Release for unix

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

src/os/exec.go

@@ -62,6 +62,9 @@ func StartProcess(name string, argv []string, attr *ProcAttr) (*Process, error)
 }
 
 func (p *Process) Wait() (*ProcessState, error) {
+	if p.Pid == -1 {
+		return nil, syscall.EINVAL
+	}
 	return nil, ErrNotImplemented
 }
 
@@ -73,6 +76,13 @@ func (p *Process) Signal(sig Signal) error {
 	return ErrNotImplemented
 }
 
+// Release releases any resources associated with the Process p,
+// rendering it unusable in the future.
+// Release only needs to be called if Wait is not.
+func (p *Process) Release() error {
+	return p.release()
+}
+
 // Keep compatibility with golang and always succeed and return new proc with pid on Linux.
 func FindProcess(pid int) (*Process, error) {
 	return findProcess(pid)

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
+}