List of lectures for the course Go, 50 quest level on JavaRush

Help patterns in CLI: app help, app <cmd> -h
Go SELF
50 level,0 lecture
We break down the UX contract of CLI help: how help differs from usage, which three help entry points users expect ( todo help, todo <cmd> -h, todo help <cmd>), how to keep a single format ( Usage/ Commands/ Flags/ Examples), and how to implement it in Go via flag.FlagSet, overriding Usage, and printing flags automatically with PrintDefaults(), while following the rule: help and errors go to stderr, command results go to stdout.
Open
Exit codes in CLI: help=0, usage=2, runtime/internal=1
Go SELF
50 level,1 lecture
We lock in a simple and predictable contract for CLI: 0 — help ( -h, help), 2 — startup error (arguments/flags/validation), 1 — runtime/internal failure. We break down why flag.ErrHelp is not usage, why os.Exit must exist only at the top level ( main()), and how to classify errors by type via usageError without relying on message text. Plus: a control-flow diagram and common mistakes.
Open
Env config in a CLI: precedence and fail fast
Go SELF
50 level,2 lecture
Let’s break down how to configure a Go CLI via environment variables and flags without any “magic”: how os.Getenv differs from os.LookupEnv, how to lock in the precedence flags > env > default, how to write small helpers ( envString, envInt), and how to validate config using the fail-fast principle. In practice, we’ll wire TODO_DATA_FILE and TODO_TIMEOUT_SEC settings into the educational todo, add friendly error messages, and mention env vars in help output.
Open
Input validation — short messages for the user
Go SELF
50 level,3 lecture
We break down why input validation is part of UX in a CLI: separating flag parsing from semantic validation, classifying errors as usage and runtime/internal, introducing the usageError type (instead of analyzing the text of err.Error()), setting up stable exit codes ( 0/ 1/ 2), and writing short “fixable” messages with a hint ( todo add -h).
Open
Reading stdin in a CLI: how to do it safely and predictably
Go SELF
50 level,4 lecture
We break down how to design reading from stdin in a CLI so the utility does not unexpectedly “hang”: input only via an explicit - protocol, unifying input through io.ReadCloser and io.NopCloser, reading one/multiple lines with bufio.Scanner, safely “read everything” via io.LimitReader, and also UX practices: separating errors into usage (exit code 2) vs runtime (exit code 1) and hints for interactive input.
Open