proxy.golang.org: failed to verify certificate

Question

When trying to build caddy docker image (caddy:2.7) the following command failed with error :

go: github.com/caddyserver/caddy/[email protected]: Get "https://proxy.golang.org/github.com/caddyserver/caddy/v2/@v/v2.7.6.info": tls: failed to verify certificate: x509: certificate signed by unknown authority

The command:

RUN xcaddy build \
    --with github.com/dunglas/mercure \
    --with github.com/dunglas/mercure/caddy \
    --with github.com/dunglas/vulcain \
    --with github.com/dunglas/vulcain/caddy

My complete Dockerfile

ARG CADDY_VERSION=2.7

FROM caddy:${CADDY_VERSION}-builder-alpine AS caddy_builder

RUN xcaddy build \
    --with github.com/dunglas/mercure \
    --with github.com/dunglas/mercure/caddy \
    --with github.com/dunglas/vulcain \
    --with github.com/dunglas/vulcain/caddy

FROM caddy:${CADDY_VERSION} AS caddy

WORKDIR /var/www/app

COPY --from=dunglas/mercure:v0.11 /srv/public /srv/mercure-assets/
COPY --from=caddy_builder /usr/bin/caddy /usr/bin/caddy
COPY docker/caddy/Caddyfile /etc/caddy/Caddyfile

Trying to build the caddy image in local: docker build -f Dockerfile --target caddy .

Expected successful build.