[Amazon.Lambda.RuntimeSupport] fix: Find header key with insensitive comparison (#2094)

Author: duncanista

.autover/changes/9f639a1b-3cd4-41ec-9d56-d6e95cb32b14.json

@@ -0,0 +1,11 @@
+{
+  "Projects": [
+    {
+      "Name": "Amazon.Lambda.RuntimeSupport",
+      "Type": "Patch",
+      "ChangelogMessages": [
+        "Fix issue making HTTP header comparisons be case insensitive"
+      ]
+    }
+  ]
+}

Libraries/src/Amazon.Lambda.RuntimeSupport/Client/RuntimeApiHeaders.cs

@@ -12,6 +12,7 @@
  * express or implied. See the License for the specific language governing
  * permissions and limitations under the License.
  */
+using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -28,12 +29,14 @@ internal class RuntimeApiHeaders
 
         public RuntimeApiHeaders(Dictionary<string, IEnumerable<string>> headers)
         {
-            DeadlineMs = GetHeaderValueOrNull(headers, HeaderDeadlineMs);
-            AwsRequestId = GetHeaderValueRequired(headers, HeaderAwsRequestId);
-            ClientContextJson = GetHeaderValueOrNull(headers, HeaderClientContext);
-            CognitoIdentityJson = GetHeaderValueOrNull(headers, HeaderCognitoIdentity);
-            InvokedFunctionArn = GetHeaderValueOrNull(headers, HeaderInvokedFunctionArn);
-            TraceId = GetHeaderValueOrNull(headers, HeaderTraceId);
+            var caseInsensitiveHeaders = new Dictionary<string, IEnumerable<string>>(headers, StringComparer.OrdinalIgnoreCase);
+
+            DeadlineMs = GetHeaderValueOrNull(caseInsensitiveHeaders, HeaderDeadlineMs);
+            AwsRequestId = GetHeaderValueRequired(caseInsensitiveHeaders, HeaderAwsRequestId);
+            ClientContextJson = GetHeaderValueOrNull(caseInsensitiveHeaders, HeaderClientContext);
+            CognitoIdentityJson = GetHeaderValueOrNull(caseInsensitiveHeaders, HeaderCognitoIdentity);
+            InvokedFunctionArn = GetHeaderValueOrNull(caseInsensitiveHeaders, HeaderInvokedFunctionArn);
+            TraceId = GetHeaderValueOrNull(caseInsensitiveHeaders, HeaderTraceId);
         }
 
         public string AwsRequestId { get; private set; }
@@ -58,5 +61,4 @@ private string GetHeaderValueOrNull(Dictionary<string, IEnumerable<string>> head
             return null;
         }
     }
-
 }