change ws.Header length int64 to uint64

[someview]

according rfc6455 chapter 5, payload length is uint16 or uint64, not int64.

[cristaloleg]

Hey, are you referring to:

If 127, the
following 8 bytes interpreted as a 64-bit unsigned integer (the
most significant bit MUST be 0) are the payload length

?

CC: @gobwas

[someview]

Hey, are you referring to:

If 127, the
following 8 bytes interpreted as a 64-bit unsigned integer (the
most significant bit MUST be 0) are the payload length

?

CC: @gobwas

You are right.