readme: update

1 files changed, 21 insertions, 1 deletions

diff --git a/README.md b/README.md
index 2bf6fe7..bbf7575 100644
--- a/README.md
+++ b/README.md
@@ -33,7 +33,7 @@ App = -> env {
   [
     200,
     { "Content-Type" => "text/plain" },
-    [" request: #{env["REQUEST_METHOD"]} #{env["PATH_INFO"]}"]
+    ["request: #{env["REQUEST_METHOD"]} #{env["PATH_INFO"]}"]
   ]
 }
 
@@ -51,6 +51,26 @@ NOTE: If `--cert` and `--key` are omitted, a temporary dummy certificate will be
 ### As a HTTP/2 (HTTP/1.x) client library
 If the server does't support HTTP/2, `Plum::Client` tries to use HTTP/1.x instead.
 
+```
+   +-----------------+
+   |:http2 option    | false
+   |(default: true)  |-------> HTTP/1.x
+   +-----------------+
+            v true
+   +-----------------+
+   |:scheme option   | "http"
+   |(default:"https")|-------> Try Upgrade from HTTP/1.1
+   +-----------------+
+            v "https"
+   +-----------------+
+   | ALPN(/NPN)      | failed
+   | negotiation     |-------> HTTP/1.x
+   +-----------------+
+            | "h2"
+            v
+          HTTP/2
+```
+
 ##### Sequential request
 ```ruby
 client = Plum::Client.start("http2.rhe.jp", 443, user_agent: "nyaan")