Fix typo, tune backoff more

async.go

@@ -176,11 +176,17 @@ var retryIntervals = []time.Duration{
 	20 * time.Minute, // elapsed: 2 hr
 	30 * time.Minute,
 	30 * time.Minute, // elapsed: 3 hr
+	30 * time.Minute,
+	30 * time.Minute, // elapsed: 4 hr
+	30 * time.Minute,
+	30 * time.Minute, // elapsed: 5 hr
+	1 * time.Hour,    // elapsed: 6 hr
 	1 * time.Hour,
-	1 * time.Hour,
-	1 * time.Hour, // elapsed: 6 hr
+	1 * time.Hour, // elapsed: 8 hr
+	2 * time.Hour,
+	2 * time.Hour, // elapsed: 12 hr
 	3 * time.Hour,
-	3 * time.Hour, // elapsed: 12 hr
+	3 * time.Hour, // elapsed: 18 hr
 	6 * time.Hour, // repeat for up to maxRetryDuration
 }
 

handshake.go

@@ -927,6 +927,6 @@ type helloInfoCtxKey string
 // a context.Context within a DecisionFunc. However, be advised that it is best practice
 // that the decision whether to obtain a certificate is be based solely on the name,
 // not other properties of the specific connection/client requesting the connection.
-// Fpr example, it is not adviseable to use a client's IP address to decide whether to
+// For example, it is not adviseable to use a client's IP address to decide whether to
 // allow a certificate. Instead, the ClientHello can be useful for logging, etc.
 const ClientHelloInfoCtxKey helloInfoCtxKey = "certmagic:ClientHelloInfo"