remove support for go1.5 (#1132)

.travis.yml

@@ -1,7 +1,6 @@
 language: go
 
 go:
-  - 1.5.4
   - 1.6.3
   - 1.7
   - 1.8
@@ -9,12 +8,12 @@ go:
 go_import_path: google.golang.org/grpc
 
 before_install:
-  - if [[ $TRAVIS_GO_VERSION != 1.5* ]]; then go get github.com/golang/lint/golint; fi
+  - go get github.com/golang/lint/golint
   - go get -u golang.org/x/tools/cmd/goimports github.com/axw/gocov/gocov github.com/mattn/goveralls golang.org/x/tools/cmd/cover
 
 script:
   - '! gofmt -s -d -l . 2>&1 | read'
   - '! goimports -l . | read'
-  - 'if [[ $TRAVIS_GO_VERSION != 1.5* ]]; then ! golint ./... | grep -vE "(_mock|_string|\.pb)\.go:"; fi'
+  - '! golint ./... | grep -vE "(_mock|_string|\.pb)\.go:"'
   - '! go tool vet -all . 2>&1 | grep -vE "constant [0-9]+ not a string in call to Errorf" | grep -vF .pb.go:' # https://github.com/golang/protobuf/issues/214
   - make test testrace

README.md

@@ -16,23 +16,7 @@ $ go get google.golang.org/grpc
 Prerequisites
 -------------
 
-This requires Go 1.5 or later.
-
-A note on the version used: significant performance improvements in benchmarks
-of grpc-go have been seen by upgrading the go version from 1.5 to the latest
-1.7.1.
-
-From https://golang.org/doc/install, one way to install the latest version of go is:
-```
-$ GO_VERSION=1.7.1
-$ OS=linux
-$ ARCH=amd64
-$ curl -O https://storage.googleapis.com/golang/go${GO_VERSION}.${OS}-${ARCH}.tar.gz
-$ sudo tar -C /usr/local -xzf go$GO_VERSION.$OS-$ARCH.tar.gz
-$ # Put go on the PATH, keep the usual installation dir
-$ sudo ln -s /usr/local/go/bin/go /usr/bin/go
-$ rm go$GO_VERSION.$OS-$ARCH.tar.gz
-```
+This requires Go 1.6 or later.
 
 Constraints
 -----------

transport/pre_go16.go

@@ -1,51 +0,0 @@
-// +build !go1.6
-
-/*
- * Copyright 2016, Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
-package transport
-
-import (
-	"net"
-	"time"
-
-	"golang.org/x/net/context"
-)
-
-// dialContext connects to the address on the named network.
-func dialContext(ctx context.Context, network, address string) (net.Conn, error) {
-	var dialer net.Dialer
-	if deadline, ok := ctx.Deadline(); ok {
-		dialer.Timeout = deadline.Sub(time.Now())
-	}
-	return dialer.Dial(network, address)
-}