Can anyone tell me is the log structure of all servers are the same?

Short answer: no.

Long answer: depends on what has been setup, if anything has been changed from defaults and what is actually running to "serve"

Windows vs Linux,
Linux distro vs Linux distro,
apache vms Nginx vs NodeJS vs other server software.

@C0D4 thanks for your answer. can you tell me where I can find sample server log data? I need access log and error log for Nginx, Lighttpd, Apache Tomcat, Caddy, Hiawatha and NodeJS. Do you know any website for this?

Not that lists all of them.

Each one would have its own documented in the official docs somewhere, otherwise spin up a server using each and extract the default logs that way.

no. It's more likely to see an apple-tree bloom at -30ºC in winter than having all components in servers logging with the same format.

Not impossible. But extremely unlikely.