public WebSocketClientBuilder allowMaskMismatch(boolean allowMaskMismatch) {
        this.allowMaskMismatch = allowMaskMismatch;
        return this;
    }
Sets whether the decoder allows to loosen the masking requirement on received frames.
It's not allowed by default.
core/src/main/java/com/linecorp/armeria/client/websocket/WebSocketClientBuilder.java