Fixing Go code style issues

[s-radyuk]

This PR introduces minor code style changes:

• improving comments for public methods to follow Go code style
• changing snake case to camel case, preferable in Go
• remove unused func parameters
• improve constants naming and grouping
• replace empty slice declaration events := []Event{} with nil slice declaration var events []Event
• improve error strings, which should not be capitalised or end with punctuation mark
• fixing some minor typos in README and comments