add travis build for go versions 1.7.x -> 1.10.x

.travis.yml

@@ -1,8 +1,30 @@
 language: go
+
+go:
+  - 1.7.x
+  - 1.8.x
+  - 1.9.x
+  - "1.10.x"
+  - master
+
+matrix:
+  # Build OK if fails on unstable development versions of Go.
+  allow_failures:
+    - go: master
+  # Don't wait for tests to finish on allow_failures.
+  # Mark the build finished if tests pass on other versions of Go.
+  fast_finish: true
+
 go_import_path: firebase.google.com/go
+
 before_install:
-    - go get github.com/golang/lint/golint
+    - go get github.com/golang/lint/golint # Golint requires Go 1.6 or later.
+
+install:
+    # Prior to golang 1.8, this can trigger an error for packages containing only tests.
+    - go get -t -v $(go list ./... | grep -v integration)
+
 script:
     - golint -set_exit_status $(go list ./...)
-    - go test -v -test.short ./...
-
+    - go test -v -race -test.short ./...        # Run tests with the race detector.
+    - go vet -v ./...                           # Run Go static analyzer.

messaging/messaging_test.go

@@ -15,7 +15,6 @@
 package messaging
 
 import (
-	"context"
 	"encoding/json"
 	"io/ioutil"
 	"net/http"
@@ -25,9 +24,9 @@ import (
 	"testing"
 	"time"
 
-	"google.golang.org/api/option"
-
 	"firebase.google.com/go/internal"
+	"golang.org/x/net/context"
+	"google.golang.org/api/option"
 )
 
 const testMessageID = "projects/test-project/messages/msg_id"

snippets/auth.go

@@ -15,12 +15,11 @@
 package snippets
 
 import (
-	"context"
 	"log"
 
 	firebase "firebase.google.com/go"
 	"firebase.google.com/go/auth"
-
+	"golang.org/x/net/context"
 	"google.golang.org/api/iterator"
 )