Provide an implementation of the Header* filters that does not depend on go1.14

plugin/othttp/filters/filters.go

@@ -126,29 +126,3 @@ func Method(m string) othttp.Filter {
 		return m == r.Method
 	}
 }
-
-// Header returns a Filter that returns true if the request
-// includes a header k with a value equal to v.
-func Header(k, v string) othttp.Filter {
-	return func(r *http.Request) bool {
-		for _, hv := range r.Header.Values(k) {
-			if v == hv {
-				return true
-			}
-		}
-		return false
-	}
-}
-
-// HeaderContains returns a Filter that returns true if the request
-// includes a header k with a value that contains v.
-func HeaderContains(k, v string) othttp.Filter {
-	return func(r *http.Request) bool {
-		for _, hv := range r.Header.Values(k) {
-			if strings.Contains(hv, v) {
-				return true
-			}
-		}
-		return false
-	}
-}

plugin/othttp/filters/header_go14.go

@@ -0,0 +1,50 @@
+// Copyright 2020, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build go1.14
+
+package filters
+
+import (
+	"net/http"
+	"strings"
+
+	"go.opentelemetry.io/otel/plugin/othttp"
+)
+
+// Header returns a Filter that returns true if the request
+// includes a header k with a value equal to v.
+func Header(k, v string) othttp.Filter {
+	return func(r *http.Request) bool {
+		for _, hv := range r.Header.Values(k) {
+			if v == hv {
+				return true
+			}
+		}
+		return false
+	}
+}
+
+// HeaderContains returns a Filter that returns true if the request
+// includes a header k with a value that contains v.
+func HeaderContains(k, v string) othttp.Filter {
+	return func(r *http.Request) bool {
+		for _, hv := range r.Header.Values(k) {
+			if strings.Contains(hv, v) {
+				return true
+			}
+		}
+		return false
+	}
+}

plugin/othttp/filters/header_nongo14.go

@@ -0,0 +1,51 @@
+// Copyright 2020, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !go1.14
+
+package filters
+
+import (
+	"net/http"
+	"net/textproto"
+	"strings"
+
+	"go.opentelemetry.io/otel/plugin/othttp"
+)
+
+// Header returns a Filter that returns true if the request
+// includes a header k with a value equal to v.
+func Header(k, v string) othttp.Filter {
+	return func(r *http.Request) bool {
+		for _, hv := range r.Header[textproto.CanonicalMIMEHeaderKey(k)] {
+			if v == hv {
+				return true
+			}
+		}
+		return false
+	}
+}
+
+// HeaderContains returns a Filter that returns true if the request
+// includes a header k with a value that contains v.
+func HeaderContains(k, v string) othttp.Filter {
+	return func(r *http.Request) bool {
+		for _, hv := range r.Header[textproto.CanonicalMIMEHeaderKey(k)] {
+			if strings.Contains(hv, v) {
+				return true
+			}
+		}
+		return false
+	}
+}