Didn't work in my laptop :(
```$ sudo docker build --build-arg http_proxy=192.168.100.4:3128/ --build-arg https_proxy=192.168.100.4:3128/ -t thibaut/devdocs .
Sending build context to Docker daemon 18.3MB
Step 1/10 : FROM ruby:2.6.0
Get registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
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