global: move to context (#1699)

* global: move to context

Move from golang.org/x/net/context to std lib's context.

Change done with:

for i in $(grep -l '/context' **/*.go); do sed -e 's|golang.org/x/net/context|context|' -i $i; echo $i; done
for i in **/*.go; do goimports -w $i; done

* drop from dns.pb.go as well

plugin/etcd/etcd.go

@@ -13,10 +13,11 @@ import (
 	"github.com/coredns/coredns/plugin/proxy"
 	"github.com/coredns/coredns/request"
 
+	"context"
+
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 	etcdc "github.com/coreos/etcd/client"
 	"github.com/miekg/dns"
-	"golang.org/x/net/context"
 )
 
 // Etcd is a plugin talks to an etcd cluster.

plugin/etcd/handler.go

@@ -5,8 +5,9 @@ import (
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
 	"github.com/coredns/coredns/request"
 
+	"context"
+
 	"github.com/miekg/dns"
-	"golang.org/x/net/context"
 )
 
 // ServeDNS implements the plugin.Handler interface.

plugin/etcd/lookup_test.go

@@ -14,9 +14,10 @@ import (
 	"github.com/coredns/coredns/plugin/proxy"
 	"github.com/coredns/coredns/plugin/test"
 
+	"context"
+
 	etcdc "github.com/coreos/etcd/client"
 	"github.com/miekg/dns"
-	"golang.org/x/net/context"
 )
 
 func init() {

plugin/etcd/setup.go

@@ -9,9 +9,10 @@ import (
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 	"github.com/coredns/coredns/plugin/proxy"
 
+	"context"
+
 	etcdc "github.com/coreos/etcd/client"
 	"github.com/mholt/caddy"
-	"golang.org/x/net/context"
 )
 
 func init() {

plugin/etcd/stub_handler.go

@@ -6,8 +6,9 @@ import (
 	"github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/request"
 
+	"context"
+
 	"github.com/miekg/dns"
-	"golang.org/x/net/context"
 )
 
 // Stub wraps an Etcd. We have this type so that it can have a ServeDNS method.

plugin/etcd/xfr.go

@@ -3,9 +3,10 @@ package etcd
 import (
 	"time"
 
+	"context"
+
 	"github.com/coredns/coredns/request"
 	"github.com/miekg/dns"
-	"golang.org/x/net/context"
 )
 
 // Serial implements the Transferer interface.