.travis.yml: move Travis to Go1.11 (census-instrumentation#172)

* Move Travis to go 1.11

We are using go.mod files to manage the packages consumed by the project,
so we need to move to go 1.11 where the feature is actually available.

* Fix gofmt when upgrading to go 1.11

.travis.yml

@@ -3,8 +3,12 @@ language: go
 go_import_path: github.com/census-instrumentation/opencensus-service
 
 go:
-  - 1.10.x
+  - 1.11.x
 
+env:
+  global:
+    GO111MODULE=on
+
 install:
   - make install-tools
-  - go get -t -v ./...
+  - go get -v ./...

receiver/zipkin/proto_parse_test.go

@@ -120,9 +120,9 @@ func TestConvertSpansToTraceSpans_protobuf(t *testing.T) {
 					Name: "svc-1",
 				},
 				Attributes: map[string]string{
-					"ipv4":        "192.168.0.1",
-					"serviceName": "svc-1",
-					"port":        "8009",
+					"ipv4":                              "192.168.0.1",
+					"serviceName":                       "svc-1",
+					"port":                              "8009",
 					"zipkin.remoteEndpoint.serviceName": "memcached",
 					"zipkin.remoteEndpoint.ipv6":        "fe80::1453:a77c:da4d:d21b",
 					"zipkin.remoteEndpoint.port":        "11211",
@@ -145,9 +145,9 @@ func TestConvertSpansToTraceSpans_protobuf(t *testing.T) {
 					Name: "search",
 				},
 				Attributes: map[string]string{
-					"ipv4":        "10.0.0.13",
-					"serviceName": "search",
-					"port":        "8009",
+					"ipv4":                              "10.0.0.13",
+					"serviceName":                       "search",
+					"port":                              "8009",
 					"zipkin.remoteEndpoint.serviceName": "redis",
 					"zipkin.remoteEndpoint.ipv6":        "fe80::1453:a77c:da4d:d21b",
 					"zipkin.remoteEndpoint.port":        "6379",