- Prints multiline fields and errors nicely

However we felt the API and developer experience could be improved.

- Compare [slog](https://godoc.org/cdr.dev/slog) to [zap](https://godoc.org/go.uber.org/zap) and

[zapcore](https://godoc.org/go.uber.org/zap/zapcore).

- The sprawling API makes zap hard to understand, use and extend.

- We found zap's fully typed API cumbersome. It does offer a

[sugared API](https://godoc.org/go.uber.org/zap#hdr-Choosing_a_Logger)

but it's too easy to pass an invalid fields list since there is no static type checking.

Furthermore, it's harder to read as there is no syntax grouping for each key value pair.

- We wanted an API that only accepted the equivalent of [zap.Any](https://godoc.org/go.uber.org/zap#Any)

for every field. This is [slog.F](https://godoc.org/cdr.dev/slog#F).

- It colors distinct parts of each line to make it easier to scan logs. Even the JSON that represents

the fields in each log is syntax highlighted so that is very easy to scan. See the screenshot above.

- zap lacks appropriate colors for different levels and fields

- slog automatically prints one multiline field after the log to make errors and such much easier to read.

- zap logs multiline fields and errors stack traces as JSON strings which made them unreadable in a terminal.

- When logging to JSON, slog automatically converts a [`golang.org/x/xerrors`](https://golang.org/x/xerrors) chain

into an array with fields for the location and wrapping messages.

- `slog` lets you set fields in a `context.Context` such that any log with the context prints those fields.

- We wanted to be able to pull up all relevant logs for a given trace, user or request. With zap, we were plugging

these fields in for every relevant log or passing around a logger with the fields set. This became very verbose.

- A new backend only has to implement the simple Sink interface.

- The Logger type provides a nice API around Sink but also implements

Sink to allow for composition.

- zap is hard and confusing to extend. There are too many structures and configuration options.

- Entire encoding process is documented on [godoc](https://godoc.org/cdr.dev/slog#Map.MarshalJSON).

- With zap, We found ourselves often implementing zap's

[ObjectMarshaler](https://godoc.org/go.uber.org/zap/zapcore#ObjectMarshaler) to log Go structures. This was

verbose and most of the time we ended up only implementing `fmt.Stringer` and using `zap.Stringer` instead.

- It marks the calling function as a helper and skips it when reporting location info.

- We had many helper functions for logging but we wanted the line reported to be of the parent function.

zap has an [API](https://godoc.org/go.uber.org/zap#AddCallerSkip) for this but it's verbose and requires

passing the logger around explicitly.

- You can configure [`slogtest`](https://godoc.org/cdr.dev/slog/sloggers/slogtest) to exit on any ERROR logs

and it has a global stateless API that takes a `testing.TB` so you do not need to create a logger first.

- Test assertion helpers are provided in [slogtest/assert](https://godoc.org/cdr.dev/slog/sloggers/slogtest/assert).

- zap has [zaptest](https://godoc.org/go.uber.org/zap/zaptest) but the API surface is large and doesn't

integrate well. It does not support any of the features described above.

RUN apt-get update

RUN apt-get install -y npm

RUN go get golang.org/x/tools/cmd/goimports

RUN go get golang.org/x/lint/golint

RUN go get github.com/mattn/goveralls