Remove support for Go1.6-1.8 (#2428)

README.md

@@ -16,7 +16,7 @@ $ go get -u google.golang.org/grpc
 Prerequisites
 -------------
 
-This requires Go 1.6 or later. Go 1.7 will be required soon.
+gRPC-Go requires Go 1.9 or later.
 
 Constraints
 -----------

benchmark/benchmark17_test.go → benchmark/benchmark_test.go

@@ -1,5 +1,3 @@
-// +build go1.7
-
 /*
  *
  * Copyright 2017 gRPC authors.

benchmark/primitives/primitives_test.go

@@ -1,5 +1,3 @@
-// +build go1.7
-
 /*
  *
  * Copyright 2017 gRPC authors.

channelz/service/func_linux.go

@@ -1,4 +1,4 @@
-// +build !appengine,go1.7
+// +build !appengine
 
 /*
  *

channelz/service/func_nonlinux.go

@@ -1,4 +1,4 @@
-// +build !linux appengine !go1.7
+// +build !linux appengine
 
 /*
  *

channelz/service/service_sktopt_test.go

@@ -1,4 +1,4 @@
-// +build linux,!appengine,go1.7
+// +build linux,!appengine
 // +build 386 amd64
 
 /*

channelz/service/service_test.go

@@ -51,6 +51,7 @@ var protoToSocketOpt protoToSocketOptFunc
 // with &utcLoc. However zero value of a time.Time type value loc field is nil.
 // This behavior will make reflect.DeepEqual fail upon unset time.Time field,
 // and cause false positive fatal error.
+// TODO: Go1.7 is no longer supported - does this need a change?
 var emptyTime time.Time
 
 type dummyChannel struct {

channelz/service/util_sktopt_386_test.go

@@ -1,4 +1,4 @@
-// +build 386,linux,!appengine,go1.7
+// +build 386,linux,!appengine
 
 /*
  *

channelz/service/util_sktopt_amd64_test.go

@@ -1,4 +1,4 @@
-// +build amd64,linux,!appengine,go1.7
+// +build amd64,linux,!appengine
 
 /*
  *

clientconn.go

@@ -19,6 +19,7 @@
 package grpc
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"math"
@@ -29,7 +30,6 @@ import (
 	"sync/atomic"
 	"time"
 
-	"golang.org/x/net/context"
 	"google.golang.org/grpc/balancer"
 	_ "google.golang.org/grpc/balancer/roundrobin" // To register roundrobin.
 	"google.golang.org/grpc/codes"
@@ -183,7 +183,7 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		cc.dopts.copts.Dialer = newProxyDialer(
 			func(ctx context.Context, addr string) (net.Conn, error) {
 				network, addr := parseDialTarget(addr)
-				return dialContext(ctx, network, addr)
+				return (&net.Dialer{}).DialContext(ctx, network, addr)
 			},
 		)
 	}

credentials/credentials.go

@@ -318,4 +318,24 @@ var cipherSuiteLookup = map[uint16]string{
 	tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384:   "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
 	tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
 	tls.TLS_FALLBACK_SCSV:                       "TLS_FALLBACK_SCSV",
+	tls.TLS_RSA_WITH_AES_128_CBC_SHA256:         "TLS_RSA_WITH_AES_128_CBC_SHA256",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
+	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256:   "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
+	tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305:    "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305",
+	tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305:  "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
+}
+
+// cloneTLSConfig returns a shallow clone of the exported
+// fields of cfg, ignoring the unexported sync.Once, which
+// contains a mutex and must not be copied.
+//
+// If cfg is nil, a new zero tls.Config is returned.
+//
+// TODO: inline this function if possible.
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+
+	return cfg.Clone()
 }

credentials/go19.go → credentials/syscall.go

@@ -1,4 +1,4 @@
-// +build go1.9,!appengine
+// +build !appengine
 
 /*
  *

encoding/proto/proto_benchmark_test.go

@@ -1,5 +1,3 @@
-// +build go1.7
-
 /*
  *
  * Copyright 2014 gRPC authors.