refactor: pin setup-gcloud gh action to v0 (#271)

diff --git a/.github/workflows/ci-v2.yaml b/.github/workflows/ci-v2.yaml
index f76cd08..47295f1 100644
--- a/.github/workflows/ci-v2.yaml
+++ b/.github/workflows/ci-v2.yaml
@@ -11,7 +11,7 @@
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: [ '1.11.x', '1.12.x', '1.13.x', '1.14.x', '1.15.x']
+        go-version: [ '1.11.x', '1.12.x', '1.13.x', '1.14.x', '1.15.x', '1.16.x']
     env:
       working-directory: ./v2
 
@@ -76,7 +76,7 @@
         restore-keys: |
           ${{ runner.os }}-${{ matrix.go-version }}-go-
     - name: Set up Cloud SDK
-      uses: google-github-actions/setup-gcloud@master
+      uses: google-github-actions/setup-gcloud@v0
     - name: Install
       working-directory: ${{env.working-directory}}
       env:
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a87d23a..ff05a20 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,7 +11,7 @@
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: [ '1.11.x', '1.12.x', '1.13.x', '1.14.x', '1.15.x']
+        go-version: [ '1.11.x', '1.12.x', '1.13.x', '1.14.x', '1.15.x', '1.16.x']
 
     steps:
     - name: Set up Go
@@ -70,7 +70,7 @@
         restore-keys: |
           ${{ runner.os }}-${{ matrix.go-version }}-go-
     - name: Set up Cloud SDK
-      uses: google-github-actions/setup-gcloud@master
+      uses: google-github-actions/setup-gcloud@v0
     - name: Install
       env:
         GO111MODULE: off
diff --git a/README.md b/README.md
index c0cf5cc..4e3f50f 100644
--- a/README.md
+++ b/README.md
@@ -72,7 +72,7 @@
 * `appengine/socket` is not required on App Engine flexible environment / Managed VMs.
   Use the standard `net` package instead.
 
-## Key Encode/Decode compatibiltiy to help with datastore library migrations
+## Key Encode/Decode compatibility to help with datastore library migrations
 
 Key compatibility updates have been added to help customers transition from google.golang.org/appengine/datastore to cloud.google.com/go/datastore.
 The `EnableKeyConversion` enables automatic conversion from a key encoded with cloud.google.com/go/datastore to google.golang.org/appengine/datastore key type.
diff --git a/v2/internal/api.go b/v2/internal/api.go
index a1c507a..96df820 100644
--- a/v2/internal/api.go
+++ b/v2/internal/api.go
@@ -67,7 +67,7 @@
 	backgroundContextOnce sync.Once
 	backgroundContext     netcontext.Context
 
-	logStream io.Writer        = os.Stdout // For test hooks.
+	logStream io.Writer        = os.Stderr // For test hooks.
 	timeNow   func() time.Time = time.Now  // For test hooks.
 )
 
diff --git a/v2/internal/log.go b/v2/internal/log.go
index e4f14ba..210df59 100644
--- a/v2/internal/log.go
+++ b/v2/internal/log.go
@@ -108,7 +108,7 @@
 }
 
 func traceAndSpan(c *context) (string, string) {
-	headers := c.req.Header["Cloud-Trace-Context"]
+	headers := c.req.Header["X-Cloud-Trace-Context"]
 	if len(headers) < 1 {
 		return "", ""
 	}
diff --git a/v2/internal/log_test.go b/v2/internal/log_test.go
index aeecb43..b724153 100644
--- a/v2/internal/log_test.go
+++ b/v2/internal/log_test.go
@@ -437,7 +437,7 @@
 		t.Fatal(err)
 	}
 	for _, h := range headers {
-		req.Header.Add("Cloud-Trace-Context", h)
+		req.Header.Add("X-Cloud-Trace-Context", h)
 	}
 	return fromContext(ContextForTesting(req))
 }