muxy: Can not start muxy proxy with a network_shape configuration.

My muxy.config:

proxy:
  - name: http_proxy
    config:
      host: 0.0.0.0
      port: 8527
      protocol: http
      proxy_host: 192.168.8.228
      proxy_port: 8527
      proxy_protocol: http
  - name: tcp_proxy
    config:
      host: 0.0.0.0           # Local address to bind to and accept connections. May be an IP/hostname
      port: 9527              # Local port to bind to
      proxy_host: 192.168.8.228     # Proxy server port
      proxy_port: 9527        # Proxied server port
      nagles_algorithm: true  # Use Nagles algorithm?
      packet_size: 64         # Size of each contiguous network packet to proxy
middleware:
  - name: logger
    config:
      hex_output: false
  - name: delay
    config:
      request_delay: 2000
      response_delay: 1500
  - name: network_shape
    config:
      latency:     1000        # Latency to add in ms
      target_bw:   10         # Bandwidth in kbits/s
      packet_loss: 0.9         # Packet loss, as a %
      target_ips:              # Target ipv4 IP addresses/CIDRs
        - "0.0.0.0/0"
      target_ips6:             # Target ipv6 IP addresses
        - "::1/128"
      target_ports:            # Target destination ports
        - "9527"               # - "1:65535"            # Ranges also valid
      target_protos:           # Target protocols
        - "tcp"
        - "udp"
        - "imp"

command

sudo ./muxy_bin proxy --config muxy_middleware.yml

logs

2018/08/21 10:38:45.999520 [INFO]		Loading plugin 	logger
2018/08/21 10:38:45.999540 [INFO]		Loading plugin 	delay
2018/08/21 10:38:45.999549 [INFO]		Loading plugin 	network_shape
2018/08/21 10:38:45.999706 [INFO]		Loading proxy 	http_proxy
2018/08/21 10:38:45.999733 [INFO]		Loading proxy 	tcp_proxy
2018/08/21 10:38:45.999741 [DEBUG]		Delay Symptom - Setup()
2018/08/21 10:38:45.999748 [DEBUG]		NetworkShaperSymptom - Setup()

and Muxy process exited.

I viewed the source code, I think that this code will has a panic:

network_shape.go - 62

executeThrottler(&s.config)

how can I solve this problem? thanks.