host is a forbidden header

src/net.ts

@@ -19,9 +19,10 @@ export interface SignedInit {
 
 // TODO: Handle redirects.
 export const signedFetch = async (url: string, init: RequestInit, signedInit: SignedInit): Promise<globalThis.Response> => {
+    const now = new Date().toUTCString();
+
     const signedHeaders: HeadersInit = [
-        ["Host", new URL(url).host],
-        ["Date", new Date().toUTCString()]
+        ["Date", now]
     ];
 
     const headerNames = ["(request-target)", "host", "date"];
@@ -52,7 +53,10 @@ export const signedFetch = async (url: string, init: RequestInit, signedInit: Si
     const signature = signer.sign({
         url,
         method: init.method as string,
-        headers: signedHeaders
+        headers: [
+            ["Host", new URL(url).host],
+            ...signedHeaders
+        ]
     });
 
     const newHeaders: HeadersInit =