Add unix domain socket support and update readme

README.md

@@ -77,3 +77,12 @@ Then use the example above changing the `DB.open` line to
 ```crystal
 DB.open "mysql://test:yourpassword@localhost/test" do |db|
 ```
+
+## Unix Domain Socket
+
+If you specify a socket path, it will override the hostname in the URI.
+
+```crystal
+DB.open "mysql://root@localhost/test?socket=/tmp/mysql.sock" do |db|
+end
+```

src/mysql/connection.cr

@@ -9,7 +9,7 @@ class MySql::Connection < DB::Connection
 
   def initialize(context : DB::ConnectionContext)
     super(context)
-    @socket = uninitialized TCPSocket
+    @socket = uninitialized TCPSocket | UNIXSocket
 
     begin
       host = context.uri.hostname || raise "no host provided"
@@ -23,8 +23,17 @@ class MySql::Connection < DB::Connection
       else
         initial_catalog = nil
       end
-
-      @socket = TCPSocket.new(host, port)
+
+      if !context.uri.query.nil?
+        params = HTTP::Params.parse(context.uri.query.to_s)
+      end
+
+      if !params.nil? && params["socket"]
+        @socket = UNIXSocket.new(params["socket"])
+      else
+        @socket = TCPSocket.new(host, port)
+      end
+
       handshake = read_packet(Protocol::HandshakeV10)
 
       write_packet(1) do |packet|