[18.03 backport] Use gometalinter; switch from x/net/context -> context

[thaJeztah]

Backport for the 18.03 branch of;

• Adding a Dockerfile and making it easy to use it for dev #2745 Adding a Dockerfile and making it easy to use it for dev
• Use gometalinter; switch from x/net/context -> context #2750 Use gometalinter; switch from x/net/context -> context
• Fix make check #2811 Fix make check

git checkout -b 18.03_backport_context upstream/bump_v18.03

# https://github.com/docker/swarmkit/pull/2745 Adding a Dockerfile and making it easy to use it for dev
git cherry-pick -s -S -x f8c048cd8c00d3530bbdd87e160c6d0a6e30ac42


# https://github.com/docker/swarmkit/pull/2750 Use gometalinter; switch from x/net/context -> context
git cherry-pick -s -S -x 318574db9d8b5953f966b7f7e0e8803fb4de03b4

git cherry-pick -s -S -x b25f50fdda5b4999e8c37d5e54725cd6734911eb
# some conflicts; see below

git cherry-pick -s -S -x 04ae7e3c35c50f0d28c27b79ccbb45db2c28f780
git cherry-pick -s -S -x 278edc28b8c4330496c01f39b72c32a054af766d
git cherry-pick -s -S -x 0e8bb705bab9c06e98dc1f23e8a5be123b002a8b
# some conflicts; see below

# https://github.com/docker/swarmkit/pull/2811 Fix make check
git cherry-pick -s -S -x 3bfc201ae805c67d604b45c2c4f48350f5873bae

conflicts in b25f50f (all trivial, in import statements);

Unmerged paths:
  (use "git add <file>..." to mark resolution)

	both modified:   agent/agent.go
	both modified:   agent/session.go
	both modified:   agent/worker.go
	both modified:   agent/worker_test.go
	both modified:   ca/certificates_test.go
	both modified:   ca/server_test.go
	both modified:   log/grpc.go
	both modified:   manager/controlapi/cluster_test.go
	both modified:   manager/controlapi/config_test.go
	both modified:   manager/controlapi/network_test.go
	both modified:   manager/controlapi/node_test.go
	both modified:   manager/controlapi/secret_test.go
	both modified:   manager/controlapi/service_test.go
	both modified:   manager/controlapi/task_test.go
	both modified:   node/node.go

conflict in (due to defaultAddrPools not being in 18.03);

diff --cc manager/manager.go
index 040f7f9f,08b158db..00000000
--- a/manager/manager.go
+++ b/manager/manager.go
@@@ -908,7 -994,20 +908,24 @@@ func (m *Manager) becomeLeader(ctx cont
        // shutdown underlying manager processes when leadership is
        // lost.
  
++<<<<<<< HEAD
 +      m.allocator, err = allocator.New(s, m.config.PluginGetter)
++=======
+       // If DefaultAddrPool is null, Read from store and check if
+       // DefaultAddrPool info is stored in cluster object
+       if m.config.NetworkConfig == nil || m.config.NetworkConfig.DefaultAddrPool == nil {
+               var cluster *api.Cluster
+               s.View(func(tx store.ReadTx) {
+                       cluster = store.GetCluster(tx, clusterID)
+               })
+               if cluster.DefaultAddressPool != nil {
+                       m.config.NetworkConfig.DefaultAddrPool = append(m.config.NetworkConfig.DefaultAddrPool, cluster.DefaultAddressPool...)
+                       m.config.NetworkConfig.SubnetSize = cluster.SubnetSize
+               }
+       }
+ 
+       m.allocator, err = allocator.New(s, m.config.PluginGetter, m.config.NetworkConfig)
++>>>>>>> 0e8bb705... gometalinter: add gosimple
        if err != nil {
                log.G(ctx).WithError(err).Error("failed to create allocator")
                // TODO(stevvooe): It doesn't seem correct here to fail

[dperny]

looks to be big failing on CI

[thaJeztah]

hm.. looks like it's failing because 18.03 uses an older version of gRPC, which is still using x/net/context; https://github.com/docker/swarmkit/blob/c23aa65fc646081600eb206c2f2dcff5a9e25143/vendor/google.golang.org/grpc/credentials/credentials.go#L49

[thaJeztah]

So, that would mean we'd have to backport #2649 🤔

[thaJeztah]

closing for now, in favour of #2877, which includes all the CI / linting fixes, but does not make the switch to context