service: on darwin add ServiceCreate option.

OS X launchd doesn't create a full session for most services.
This may be a performance or security decision. Regardless
in order to create a full user session for a service set
this option to true. Leaving as false as this is the os
and historical default.

service.go

@@ -76,6 +76,8 @@ const (
 	optionRunAtLoadDefault     = false
 	optionUserService          = "UserService"
 	optionUserServiceDefault   = false
+	optionSessionCreate        = "SessionCreate"
+	optionSessionCreateDefault = false
 )
 
 // Config provides the setup for a Service. The Name field is required.

service_darwin.go

@@ -5,6 +5,7 @@
 package service
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"os/signal"
@@ -13,7 +14,6 @@ import (
 	"syscall"
 	"text/template"
 	"time"
-	"errors"
 )
 
 const maxPathSize = 32 * 1024
@@ -134,11 +134,13 @@ func (s *darwinLaunchdService) Install() error {
 		Path string
 
 		KeepAlive, RunAtLoad bool
+		SessionCreate        bool
 	}{
 		Config:        s.Config,
 		Path:          path,
 		KeepAlive:     s.Option.bool(optionKeepAlive, optionKeepAliveDefault),
 		RunAtLoad:     s.Option.bool(optionRunAtLoad, optionRunAtLoadDefault),
+		SessionCreate: s.Option.bool(optionSessionCreate, optionSessionCreateDefault),
 	}
 
 	functions := template.FuncMap{
@@ -229,6 +231,7 @@ var launchdConfig = `<?xml version='1.0' encoding='UTF-8'?>
 {{if .UserName}}<key>UserName</key><string>{{html .UserName}}</string>{{end}}
 {{if .ChRoot}}<key>RootDirectory</key><string>{{html .ChRoot}}</string>{{end}}
 {{if .WorkingDirectory}}<key>WorkingDirectory</key><string>{{html .WorkingDirectory}}</string>{{end}}
+<key>SessionCreate</key><{{bool .SessionCreate}}/>
 <key>KeepAlive</key><{{bool .KeepAlive}}/>
 <key>RunAtLoad</key><{{bool .RunAtLoad}}/>
 <key>Disabled</key><false/>