APISprout in Docker Image can't download an OpenAPI file from a SSL Web server that is signed with a private authority.
$ ./apisprout https://localhost:8080/api.yml
2020/02/05 23:08:28 Get https://localhost:8080/api.yml: x509: certificate signed by unknown authority
However update-ca-certificates is present into the image (see Dockerfile).
I suggest you to modify the Dockerfile to run update-ca-certificates at APISprout startup by replacing
ENTRYPOINT ["/usr/local/bin/apisprout"]
with
COPY startup.sh /startup.sh
RUN chmod +x /startup.sh
ENTRYPOINT [ "/startup.sh" ]
and adding this new startup.sh file:
#!/bin/sh
update-ca-certificates
/startup.sh