Moved the ErrProcessDone variable to common place and removed duplicates

Signed-off-by: Alwin Doss <[email protected]>

Author: alwindoss

src/os/exec.go

@@ -5,6 +5,7 @@
 package os
 
 import (
+	"errors"
 	"internal/testlog"
 	"runtime"
 	"sync"
@@ -13,6 +14,9 @@ import (
 	"time"
 )
 
+// ErrProcessDone indicates a Process has finished.
+var ErrProcessDone = errors.New("os: process already finished")
+
 // Process stores the information about a process created by StartProcess.
 type Process struct {
 	Pid    int

src/os/exec_plan9.go

@@ -5,7 +5,6 @@
 package os
 
 import (
-	"errors"
 	"runtime"
 	"syscall"
 	"time"
@@ -50,9 +49,6 @@ func (p *Process) writeProcFile(file string, data string) error {
 	return e
 }
 
-// ErrProcessDone indicates a Process has finished.
-var ErrProcessDone = errors.New("os: process already finished")
-
 func (p *Process) signal(sig Signal) error {
 	if p.done() {
 		return ErrProcessDone

src/os/exec_unix.go

@@ -59,9 +59,6 @@ func (p *Process) wait() (ps *ProcessState, err error) {
 	return ps, nil
 }
 
-// ErrProcessDone indicates a Process has finished.
-var ErrProcessDone = errors.New("os: process already finished")
-
 func (p *Process) signal(sig Signal) error {
 	if p.Pid == -1 {
 		return errors.New("os: process already released")

src/os/exec_windows.go

@@ -55,9 +55,6 @@ func terminateProcess(pid, exitcode int) error {
 	return NewSyscallError("TerminateProcess", e)
 }
 
-// ErrProcessDone indicates a Process has finished.
-var ErrProcessDone = errors.New("os: process already finished")
-
 func (p *Process) signal(sig Signal) error {
 	handle := atomic.LoadUintptr(&p.handle)
 	if handle == uintptr(syscall.InvalidHandle) {