by joamaki:

Websocket's Read() method returns os.E2BIG if the message doesn't fit
the buffer. The JSON decoder doesn't handle this and returns the error
to the caller.

I'm currently working around this with:

--- a/src/pkg/json/stream.go    Mon Sep 27 11:42:58 2010 +1000
+++ b/src/pkg/json/stream.go    Mon Sep 27 10:25:10 2010 +0300
@@ -107,7 +107,17 @@
 
        // Read.  Delay error for next iteration (after scan).
        var n int
-       n, err = dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
+       for {
+           n, err = dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
+           if err == os.E2BIG {
+               newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
+               copy(newBuf, dec.buf)
+               dec.buf = newBuf
+               continue
+           }
+           break
+       }
+
        dec.buf = dec.buf[0 : len(dec.buf)+n]
    }
    return scanp, nil