replace log with logrus

[glightfoot]

This replaces the std lib log with logrus to enable structured logging and levels. I attempted to guess what levels things should live at, as well as moved some things to structured fields, and changed the default output to stderr.

I can't get the tests to run correctly on my machine as they hang forever, but it seems to work.

Fixes #46

[kruskall]

I think zap would be a better/faster alternative

See sirupsen/logrus@4ecd9a6

[glightfoot]

While zap is definitely faster, this only has a few calls and the performance difference is negligible. Logrus is in maintenance mode, but is stable and shouldn't need any updates. In this case, I think it makes for a simpler swap, but I opened #55 to show what it would look like with zap.

[glightfoot]

Here's some example output (all to stderr):

$ dist/gci print pkg/gci/format.go --debug >/dev/null 
DEBUG[2022-03-10T14:31:49-08:00] Loaded file                                   file=pkg/gci/format.go
DEBUG[2022-03-10T14:31:49-08:00] Parsed imports in file                        imports="[\"bytes\" \"fmt\" \"strings\" \"github.com/daixiang0/gci/pkg/constants\" \"github.com/daixiang0/gci/pkg/gci/imports\" \"github.com/daixiang0/gci/pkg/gci/sections\" \"github.com/daixiang0/gci/pkg/gci/specificity\" \"github.com/sirupsen/logrus\"]"
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"bytes\"" section=Standard
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"fmt\"" section=Standard
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"strings\"" section=Standard
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"github.com/daixiang0/gci/pkg/constants\"" section=Default
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"github.com/daixiang0/gci/pkg/gci/imports\"" section=Default
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"github.com/daixiang0/gci/pkg/gci/sections\"" section=Default
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"github.com/daixiang0/gci/pkg/gci/specificity\"" section=Default
DEBUG[2022-03-10T14:31:49-08:00] Matched import to section                     import="\"github.com/sirupsen/logrus\"" section=Default
DEBUG[2022-03-10T14:31:49-08:00] Formatting section with imports               imports="[\"bytes\" \"fmt\" \"strings\"]" section=Standard
DEBUG[2022-03-10T14:31:49-08:00] Formatting section with imports               imports="[\"github.com/daixiang0/gci/pkg/constants\" \"github.com/daixiang0/gci/pkg/gci/imports\" \"github.com/daixiang0/gci/pkg/gci/sections\" \"github.com/daixiang0/gci/pkg/gci/specificity\" \"github.com/sirupsen/logrus\"]" section=Default

[glightfoot]

With the pretty print funcs, the output looks like this:

$ dist/gci print pkg/gci/format.go --debug  >/dev/null 
DEBUG[2022-03-10T14:49:50-08:00] Loaded file                                   file=pkg/gci/format.go
DEBUG[2022-03-10T14:49:50-08:00] Parsed imports in file                        imports="[bytes fmt strings github.com/daixiang0/gci/pkg/constants github.com/daixiang0/gci/pkg/gci/imports github.com/daixiang0/gci/pkg/gci/sections github.com/daixiang0/gci/pkg/gci/specificity github.com/sirupsen/logrus]"
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=bytes section=Standard
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=fmt section=Standard
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=strings section=Standard
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=github.com/daixiang0/gci/pkg/constants section=Default
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=github.com/daixiang0/gci/pkg/gci/imports section=Default
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=github.com/daixiang0/gci/pkg/gci/sections section=Default
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=github.com/daixiang0/gci/pkg/gci/specificity section=Default
DEBUG[2022-03-10T14:49:50-08:00] Matched import to section                     import=github.com/sirupsen/logrus section=Default
DEBUG[2022-03-10T14:49:50-08:00] Formatting section with imports               imports="[bytes fmt strings]" section=Standard
DEBUG[2022-03-10T14:49:50-08:00] Formatting section with imports               imports="[github.com/daixiang0/gci/pkg/constants github.com/daixiang0/gci/pkg/gci/imports github.com/daixiang0/gci/pkg/gci/sections github.com/daixiang0/gci/pkg/gci/specificity github.com/sirupsen/logrus]" section=Default

[daixiang0]

Here we can support more levels more than debug.

[daixiang0]

Looks good overall, logrus is enough for now.

[daixiang0]

@glightfoot thanks for your contribution!

[ldez]

Hello, the problems with logrus are:

• a large dependencies graph
• when using gci as a library, because the logger is a singleton, it can be complex to setup.

In 99% of cases when you create a library, the init function must be prohibited.

It's better to create an abstraction around the logger with an interface and set up the logger in the main function instead of an init function.