Delve Debugger

Set breakpoints, inspect variables, trace goroutines, and step through code with Go's purpose-built debugger.

8 min readProgramming Foundations (Go)Code

Installing Delve

Delve (dlv) is the standard Go debugger. It understands goroutines, deferred functions, and Go's calling conventions in a way that generic debuggers like gdb do not.

Install Delve


go install github.com/go-delve/delve/cmd/dlv@latest
dlv version

Starting a Debug Session

Command	When to use
`dlv debug ./cmd/myapp`	Build and debug in one step (most common)
`dlv test ./pkg`	Debug a specific test package
`dlv exec ./myapp`	Debug an already-built binary
`dlv attach <pid>`	Attach to a running process
`dlv connect :2345`	Connect to a headless Delve server

Starting a debug session


# Debug the main package
dlv debug .

# Debug a test
dlv test ./internal/task -- -run TestAdd

# VS Code: launch.json (press F5)
# {
#   "type": "go",
#   "request": "launch",
#   "program": "${workspaceFolder}/cmd/myapp"
# }

Breakpoints and Stepping

Set a breakpoint at a file:line or a function name. Once paused, step through code one line at a time or step into function calls.

Core Delve commands


(dlv) break main.main           # breakpoint at function
(dlv) break main.go:42          # breakpoint at line
(dlv) continue                  # run until next breakpoint (alias: c)
(dlv) next                      # step over (next line, alias: n)
(dlv) step                      # step into function call (alias: s)
(dlv) stepout                   # finish current function and return
(dlv) list                      # show current source location
(dlv) clearall                  # remove all breakpoints

Inspecting State

Once paused at a breakpoint, inspect variables, evaluate expressions, and examine goroutines without modifying any code.

Inspecting variables and goroutines


(dlv) locals                    # all local variables
(dlv) print variableName        # print a specific variable (alias: p)
(dlv) print myMap["key"]        # evaluate expressions
(dlv) whatis variableName       # show the type of a variable

(dlv) goroutines                # list all goroutines
(dlv) goroutine 3               # switch to goroutine 3
(dlv) stack                     # current goroutine stack trace
(dlv) frame 2                   # switch to stack frame 2

(dlv) watch -w myVar            # watchpoint: break when myVar changes

Use Delve from VS Code

The Go extension for VS Code integrates Delve seamlessly. Set breakpoints by clicking the gutter, press F5 to start debugging, and use the Variables panel instead of typing print. This is faster for most debugging sessions than the command-line interface.

Goa-small-program-to-debug.go

18 linesLn 1, Col 1Go

Set a breakpoint on `fibonacci` and watch `n` decrease as the recursion unwinds. Use `stack` to see the call depth build up.

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

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Testing & Debugging in Go