How to dump goroutine stacktraces?

There is an HTTP frontend for the runtime/pprof package mentioned in Intermernet's answer. Import the net/http/pprof package to register an HTTP handler for /debug/pprof:

import _ "net/http/pprof"
import _ "net/http"

Start an HTTP listener if you do not have one already:

go func() {
    log.Println(http.ListenAndServe("localhost:6060", nil))
}()

Then point a browser to http://localhost:6060/debug/pprof for a menu, or http://localhost:6060/debug/pprof/goroutine?debug=2 for a full goroutine stack dump.

There are other fun things you can learn about your running code this way too. Check out the blog post for examples and more details: http://blog.golang.org/profiling-go-programs

To print the stack trace for the current goroutine, use PrintStack() from runtime/debug.

PrintStack prints to standard error the stack trace returned by Stack.

For example:

import(
   "runtime/debug"
)
...    
debug.PrintStack()

To print the stack trace for all goroutines use Lookup and WriteTo from runtime/pprof.

func Lookup(name string) *Profile
// Lookup returns the profile with the given name,
// or nil if no such profile exists.

func (p *Profile) WriteTo(w io.Writer, debug int) error
// WriteTo writes a pprof-formatted snapshot of the profile to w.
// If a write to w returns an error, WriteTo returns that error.
// Otherwise, WriteTo returns nil.

Each Profile has a unique name. A few profiles are predefined:

goroutine - stack traces of all current goroutines
heap - a sampling of all heap allocations
threadcreate - stack traces that led to the creation of new OS threads
block - stack traces that led to blocking on synchronization primitives

For example:

pprof.Lookup("goroutine").WriteTo(os.Stdout, 1)