WIP: Use pure go sqlite driver instead of cgo go-sqlite3 and remove go build tags related with sqlite

[lunny]

This PR tries to use pure go sqlite driver instead of cgo go-sqlite3 for better compile time.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs during the next 2 months. Thank you for your contributions.

[delvh]

I have two questions:

1. Why does this library bring its own C library?
2. How does adding far more code improve compile time?

[wxiaoguang]

That's GO styling. GO standard says: every error message starts with lower-case. Please read the standards.

[wxiaoguang]

Google it: https://github.com/golang/go/wiki/CodeReviewComments#error-strings

[lunny]

I have two questions:

1. Why does this library bring its own C library?
2. How does adding far more code improve compile time?

1. I think since the pure go sqlite library was translated from original sqlite, so the author also translate them. Maybe he will change them at some point.
2. This is a CGO problem. When compile with CGO, the Go compiler will spend more time. But when compile a pure Go project which even has more source files, it's faster.

[wxiaoguang]

After reading the code of modernc.org/sqlite, I'd like to say, it's surprisingly interesting and extremely impressive (well, I can not find other words to describe it because I only know a few words to describe an awesome thing ...)

The modernc/sqlite team wrote a C99 compiler frontend in Go, and wrote a lot of cross-platform code for their Go-based libc, then they compile the sqlite official code by their C compiler using their libc into Go, and embed it into the modernc/sqlite ....

ps: I haven't done any test and I am not sure how much time could be save by this Go-sqlite during Gitea compiling, just leave a comment about how it works.

[lunny]

After reading the code of modernc.org/sqlite, I'd like to say, it's surprisingly interesting and extremely impressive (well, I can not find other words to describe it because I only know a few words to describe an awesome thing ...)

The modernc/sqlite team wrote a C99 compiler frontend in Go, and wrote a lot of cross-platform code for their Go-based libc, then they compile the sqlite official code by their C compiler using their libc into Go, and embed it into the modernc/sqlite ....

ps: I haven't done any test and I am not sure how much time could be save by this Go-sqlite during Gitea compiling, just leave a comment about how it works.

I think much time and memory in developer's machine and CI agents will be saved when CGO is gone. Because we can drop the xgo to do cross-compile. When using xgo, you have to check or download a very big image(about 5GB) and spent many time to compile because c++ compile is slower than pure Go.