JSON to Go Struct

From sample JSON to typed Go structs

Go has no dynamic maps-of-anything that are pleasant to work with, so decoding JSON idiomatically means defining a struct with field types and json: tags. Writing those by hand for a large payload is tedious and error prone. A generator reads one representative sample and infers the struct layout, including nested types for objects and slices for arrays.

Example

Input:

{ "user_id": 7, "name": "Ada", "tags": ["a"] }

Generated Go:

type AutoGenerated struct {
	UserID int      `json:"user_id"`
	Name   string   `json:"name"`
	Tags   []string `json:"tags"`
}

Note how user_id becomes the exported field UserID while the tag keeps the original snake_case key. Exported (capitalized) fields are required or encoding/json cannot populate them.

Pitfalls the sample cannot show

Inference only knows what is in the sample. A field that is null or absent in your example gives the generator nothing to work with, so it may guess interface or omit the field. Numbers are the other trap: JSON has one number type, so 1 infers as int even when the real data later contains 1.5. If a field can be fractional, widen it to float64 by hand.

FAQ

Should I add omitempty? Add it to fields that are optional on output so Go skips zero values during marshaling. The generator cannot know your intent, so this is a manual pass.

How do I handle a field that is sometimes a string and sometimes a number? Mixed-type JSON forces json.RawMessage or a custom UnmarshalJSON. Generators flag these as interface at best.

What about Python or Rust? See JSON to Python and JSON to Rust for the same idea in other languages.