Can't unmarshall env variable with multiple words

[efiShtain]

Describe the bug Can't get env variable unmarshalling to work if the env variable has multiple words in it

This is not matched correctly with the following example

MYVAR_GOOGLE_IS_ENABLED: "true"

To Reproduce

package main

import (
    "fmt"
    "strings"

    "github.com/knadh/koanf/providers/env"
    "github.com/knadh/koanf/v2"
)

type Config struct {
    Google struct {
        IsEnabled bool `koanf:"is.enabled"`
    } `koanf:"google"`
}

func main() {
    k := koanf.New(".")
    prefix := "MYVAR_"
    if err := k.Load(env.Provider(prefix, ".", func(s string) string {
        return strings.Replace(strings.ToLower(
            strings.TrimPrefix(s, prefix)), "_", ".", -1)
    }), nil); err != nil {
        panic(err)
    }

    var cfg Config
    if err := k.Unmarshal("", &cfg); err != nil {
        fmt.Printf("error unmarshalling config: %v\n", err)
        return
    }

    fmt.Println("Google is enabled:", cfg.Google.IsEnabled)
}

Result is false

Expected behavior cfg.Google.IsEnabled should be true

Please provide the following information):

• OS: [e.g. linux/osx/windows]
• Koanf Version [e.g. v1.0.0]

Additional context Add any other context about the problem here.