auth not working ?

[changchichung]

my config

listen="0.0.0.0:3129"
access_log="/tmp/microproxy.access.log"
activity_log="/tmp/microproxy.error.log"
allowed_connect_ports=[443, 80]
auth_file="auth.txt"
auth_type="basic"
auth_realm="proxy"
forwarded_for_header="on"
#allowed_networks=["127.0.0.1/32"]
#add_headers=[
#	["X-Test-Header1", "yes"],
#	["X-Test-Header2", "no"]
#]

auth.txt

user:password

even I already add auth_type in config , but client still can connect to microproxy without authencation . any suggestions ?