CLI Project Plan

Design a task tracker CLI from scratch — define commands, flags, data shapes, and the package structure before writing a line of code.

6 min readProgramming Foundations (Go)Code

What We Are Building

Over the next six lessons we will build tasker — a command-line task tracker. It will store tasks as JSON, support adding, listing, completing, and deleting tasks, and ship as a single static binary.

Why a CLI?

Command-line tools are the perfect beginner project: they exercise reading input, parsing flags, working with files, handling errors, and producing clean output — all without the complexity of a network server or a UI framework. Every SRE tool you will build professionally is a CLI.

Commands and Flags

A well-designed CLI has a consistent command structure. Subcommands group related operations; flags modify their behaviour. The UNIX convention is tool verb [flags] [arguments].

Command	Flags	Effect
`tasker add`	`-title "Buy milk" -tag shopping`	Create a new task
`tasker list`	`-tag shopping -done false`	List tasks, optionally filtered
`tasker done`	`-id <id>`	Mark a task complete
`tasker delete`	`-id <id>`	Remove a task
`tasker help`	—	Print usage information

Data Shape

Define the data shape before writing any code. This forces you to think about what information you actually need and what the JSON storage will look like.

Gotask-data-model.go

18 linesLn 1, Col 1Go

`DoneAt` is a pointer to `time.Time` so it can be `null` in JSON when the task is not yet done. The `omitempty` tag skips empty slices and nil pointers during marshalling, keeping the JSON clean.

Package Structure

A small but real project layout: cmd/tasker holds main.go; internal/task holds the data model and storage logic; internal/cli handles command parsing.

Creating the project layout


mkdir -p tasker/cmd/tasker
mkdir -p tasker/internal/task
mkdir -p tasker/internal/cli

cd tasker
go mod init github.com/thesyscoder/tasker

# Result:
# tasker/
#   cmd/tasker/main.go       ← entry point
#   internal/task/task.go    ← data model
#   internal/task/store.go   ← file-based storage
#   internal/cli/commands.go ← command handlers
#   go.mod

The internal/ prefix restricts imports to this module only. Splitting task (data) from cli (presentation) follows the separation-of-concerns principle and makes each part independently testable.

cmd/tasker/main.go — parses the subcommand and delegates to cli.
internal/task/task.go — defines Task and Tasks types.
internal/task/store.go — reads and writes tasks.json with proper locking.
internal/cli/commands.go — one function per subcommand: Add, List, Done, Delete.

Mark this lesson complete to store local progress and unlock a cleaner resume path the next time you visit.

Stage 1 · Code

Your First Real Program