Installing libopenapi

import (
    "fmt"
    "github.com/pb33f/libopenapi"
    "os"
)

func readSpec() {

    // load an OpenAPI 3 specification from bytes
    petstore, _ := os.ReadFile("test_specs/petstorev3.json")

    // create a new document from specification bytes
    document, err := libopenapi.NewDocument(petstore)

    // if anything went wrong, an error is thrown
    if err != nil {
        panic(fmt.Sprintf("cannot create new document: %e", err))
    }

    // because we know this is a v3 spec, we can build a ready to go model from it.
    v3Model, err := document.BuildV3Model()

    // if anything went wrong when building the v3 model, errors (will be joined) are returned
    if err != nil {
        panic(fmt.Sprintf("cannot create v3 model from document: %e", err))
    }

    // get a count of the number of paths and schemas.
    paths := v3Model.Model.Paths.PathItems.Len()
    schemas := v3Model.Model.Components.Schemas.Len()

    // print the number of paths and schemas in the document
    fmt.Printf("There are %d paths and %d schemas in the document", paths, schemas)
}