@Override
    public Object setAttributeIfAbsent(final String key, final Object value) {
        return this.ch.attr(AttributeKey.valueOf(key)).setIfAbsent(value);
    }
Get netty channel.

@author jiachun.fjc
jraft-extension/rpc-grpc-impl/src/main/java/io/grpc/netty/shaded/io/grpc/netty/NettyConnectionHelper.java