davecgh/go-spew

$ go get -u github.com/davecgh/go-spew/spew

import "github.com/davecgh/go-spew/spew"

spew.Dump(myVar1, myVar2, ...)
spew.Fdump(someWriter, myVar1, myVar2, ...)
str := spew.Sdump(myVar1, myVar2, ...)

spew.Printf("myVar1: %v -- myVar2: %+v", myVar1, myVar2)
spew.Printf("myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
spew.Fprintf(someWriter, "myVar1: %v -- myVar2: %+v", myVar1, myVar2)
spew.Fprintf(someWriter, "myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)

package main

import (
    "fmt"
    "html"
    "net/http"

    "github.com/davecgh/go-spew/spew"
)

func handler(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "text/html")
    fmt.Fprintf(w, "Hi there, %s!", r.URL.Path[1:])
    fmt.Fprintf(w, "<!--\n" + html.EscapeString(spew.Sdump(w)) + "\n-->")
}

func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":8080", nil)
}

(main.Foo) {
 unexportedField: (*main.Bar)(0xf84002e210)({
  flag: (main.Flag) flagTwo,
  data: (uintptr) <nil>
 }),
 ExportedField: (map[interface {}]interface {}) {
  (string) "one": (bool) true
 }
}
([]uint8) {
 00000000  11 12 13 14 15 16 17 18  19 1a 1b 1c 1d 1e 1f 20  |............... |
 00000010  21 22 23 24 25 26 27 28  29 2a 2b 2c 2d 2e 2f 30  |!"#$%&'()*+,-./0|
 00000020  31 32                                             |12|
}

	  %v: <**>5
	 %+v: <**>(0xf8400420d0->0xf8400420c8)5
	 %#v: (**uint8)5
	%#+v: (**uint8)(0xf8400420d0->0xf8400420c8)5

	  %v: <*>{1 <*><shown>}
	 %+v: <*>(0xf84003e260){ui8:1 c:<*>(0xf84003e260)<shown>}
	 %#v: (*main.circular){ui8:(uint8)1 c:(*main.circular)<shown>}
	%#+v: (*main.circular)(0xf84003e260){ui8:(uint8)1 c:(*main.circular)(0xf84003e260)<shown>}

* Indent
	String to use for each indentation level for Dump functions.
	It is a single space by default.  A popular alternative is "\t".

* MaxDepth
	Maximum number of levels to descend into nested data structures.
	There is no limit by default.

* DisableMethods
	Disables invocation of error and Stringer interface methods.
	Method invocation is enabled by default.

* DisablePointerMethods
	Disables invocation of error and Stringer interface methods on types
	which only accept pointer receivers from non-pointer variables.  This option
	relies on access to the unsafe package, so it will not have any effect when
	running in environments without access to the unsafe package such as Google
	App Engine or with the "safe" build tag specified.
	Pointer method invocation is enabled by default.

* DisablePointerAddresses
	DisablePointerAddresses specifies whether to disable the printing of
	pointer addresses. This is useful when diffing data structures in tests.

* DisableCapacities
	DisableCapacities specifies whether to disable the printing of capacities
	for arrays, slices, maps and channels. This is useful when diffing data
	structures in tests.

* ContinueOnMethod
	Enables recursion into types after invoking error and Stringer interface
	methods. Recursion after method invocation is disabled by default.

* SortKeys
	Specifies map keys should be sorted before being printed. Use
	this to have a more deterministic, diffable output.  Note that
	only native types (bool, int, uint, floats, uintptr and string)
	and types which implement error or Stringer interfaces are supported,
	with other types sorted according to the reflect.Value.String() output
	which guarantees display stability.  Natural map order is used by
	default.

* SpewKeys
	SpewKeys specifies that, as a last resort attempt, map keys should be
	spewed to strings and sorted by those strings.  This is only considered
	if SortKeys is true.