gitlab keep asking username and password when cloning public project via https

gitlab keep asking username and password when cloning public project via https

i encountered this error on docker container

my Dockerfile is :

FROM golang:1.6.3

ADD my-gitlab.crt /usr/local/share/ca-certificates/my-gitlab.crt

RUN update-ca-certificates

and

[root@localhost] docker build -t my-docker -f Dockerfile .

[root@localhost] docker run -it my-docker /bin/bash

Sending build context to Docker daemon 6.656 kB

Step 1 : FROM golang:1.6.3

---> f24c8478ed40

Step 2 : ADD my-gitlab.crt /usr/local/share/ca-certificates/my-gitlab.crt

---> Using cache

---> 8157e5a037e9

Step 3 : RUN update-ca-certificates

---> Using cache

---> 156a64cc78e0

Successfully built 156a64cc78e0

root@86b1446c036f:/go# git clone https://mygitlab.public.project.git

Cloning into 'mygitlab.public.project'...

Username for 'https://mygitlab':

i can not understand why gitlab ask authentication information even if the project is public!

gitlab version : GitLab Community Edition 8.13.4 36250244