Interfaces in Go vs TS

interface Geometry {
  area(): number;
}

class Rect implements Geometry {
  constructor(private height: number, private width: number) {}
  area(): number {
    return this.height * this.width;
  }
}

class Circle implements Geometry {
  constructor(private radius: number) {}
  area(): number {
    return Math.PI * this.radius * this.radius;
  }
}

class Triangle implements Geometry {
  constructor(private base: number, private height: number) {}
  area(): number {
    return (this.base * this.height) / 2.0;
  }
}

function measure(g: Geometry): void {
  console.log('area :', g.area());
}

const r = new Rect(3, 4);
const c = new Circle(5);
const t = new Triangle(5, 6);

measure(r);
measure(c);
measure(t);

package main

import (
    "fmt"
    "math"
)

type geometry interface {
    area() float64
}

type rect struct {
    width, height float64
}

type circle struct {
    radius float64
}

type triangle struct {
    base, height float64
}

func (r rect) area() float64 {
    return r.width * r.height
}

func (c circle) area() float64 {
    return math.Pi * c.radius * c.radius
}

func (t triangle) area() float64 {
    return (t.base * t.height)/2
}

func measure(g geometry) {
  fmt.Println(g)
    fmt.Println("area :", g.area())
}

func main() {
    r := rect{width: 3, height: 4}
    c := circle{radius: 5}
    t := triangle{base:5, height: 6}

    measure(r)
    measure(c)
    measure(t)
}