Revert "Updated gRPC vendoring to support Keep Alive"

vendor/golang.org/x/net/proxy/proxy.go

@@ -11,7 +11,6 @@ import (
 	"net"
 	"net/url"
 	"os"
-	"sync"
 )
 
 // A Dialer is a means to establish a connection.
@@ -28,7 +27,7 @@ type Auth struct {
 // FromEnvironment returns the dialer specified by the proxy related variables in
 // the environment.
 func FromEnvironment() Dialer {
-	allProxy := allProxyEnv.Get()
+	allProxy := os.Getenv("all_proxy")
 	if len(allProxy) == 0 {
 		return Direct
 	}
@@ -42,7 +41,7 @@ func FromEnvironment() Dialer {
 		return Direct
 	}
 
-	noProxy := noProxyEnv.Get()
+	noProxy := os.Getenv("no_proxy")
 	if len(noProxy) == 0 {
 		return proxy
 	}
@@ -93,42 +92,3 @@ func FromURL(u *url.URL, forward Dialer) (Dialer, error) {
 
 	return nil, errors.New("proxy: unknown scheme: " + u.Scheme)
 }
-
-var (
-	allProxyEnv = &envOnce{
-		names: []string{"ALL_PROXY", "all_proxy"},
-	}
-	noProxyEnv = &envOnce{
-		names: []string{"NO_PROXY", "no_proxy"},
-	}
-)
-
-// envOnce looks up an environment variable (optionally by multiple
-// names) once. It mitigates expensive lookups on some platforms
-// (e.g. Windows).
-// (Borrowed from net/http/transport.go)
-type envOnce struct {
-	names []string
-	once  sync.Once
-	val   string
-}
-
-func (e *envOnce) Get() string {
-	e.once.Do(e.init)
-	return e.val
-}
-
-func (e *envOnce) init() {
-	for _, n := range e.names {
-		e.val = os.Getenv(n)
-		if e.val != "" {
-			return
-		}
-	}
-}
-
-// reset is used by tests
-func (e *envOnce) reset() {
-	e.once = sync.Once{}
-	e.val = ""
-}