Do not use apt as it is meant to be an end-user tool, use apt-get or apt-cache instead.

Problematic code:

FROM busybox
RUN apt install curl=1.1.0

Correct code:

FROM busybox
RUN apt-get install curl=1.1.0

Rationale:

apt is discouraged by the linux distributions as an unattended tool as its interface may suffer changes between versions. Better use the more stable apt-get and apt-cache