change fields function to return interface{}
add formator
link formater and fields to the logging system
fix formater wrong
using a log struct to store each log
fix richformat error
move calldepth value to the genRuntime function
errorString -> errString
generate short function name
use goroutine for file writing, rather than others

this makes the system able to generate runtime information
revise fields_test based on the API changing in fields.go
delete module name from richformat
fix typo
clean code
use path.Base instead of parsing string
clean code
genLog doesn't need lock
update example
fix seqid issue
add seqid to richformat