我是否需要使用nginx或Apache才能使用Lets Encrypt？

I have a really simple API based on golang that just listens at a path and responds accordingly with a database insert.

I want to serve it over TLS/https using Lets Encrypt, but all the tutorials seem to indicate use of Apache or nginx as a requirement.

I like keeping my server really light and haven't seen any need to introduce the overhead of these web servers (it's definitely not a full fledged website) and over http my go implementation works well.

Is it possible to install it without Apache or nginx?

No, you do not need to use Apache/Nginx, Go handles TLS just fine.

Check http.ListenAndServeTLS

Example:

➜ sudo letsencrypt certonly --standalone --agree-tos --email you@email.com -d domain1.com [-d domain2.com, etc..]
➜ sudo cat /etc/letsencrypt/archive/domain1.com/fullchain1.pem > cert.pem
➜ sudo cat /etc/letsencrypt/archive/domain1.com/privkey1.pem > key.pem 

➜ cat main.go
import (
    "log"
    "net/http"
)

func handler(w http.ResponseWriter, req *http.Request) {
    w.Header().Set("Content-Type", "text/plain")
    w.Write([]byte("This is an example server.
"))
}

func main() {
    http.HandleFunc("/", handler)
    log.Printf("About to listen on 10443. Go to https://domain1.com:10443/")
    log.Fatal(http.ListenAndServeTLS(":10443", "cert.pem", "key.pem", nil))
}

Note that if you want your go server to listen on port 443 (default https port), you will either have to run it as root or use systemd to pass it the port.

Example of running on port 443:

1. Change the code to log.Fatal(http.ListenAndServeTLS(":443", "cert.pem", "key.pem", nil))

2. go build

3. sudo ./your-package-name
4. or if you don't want to run as root, you will have to chown cert.pem/key.pem as your user then run setcap cap_net_bind_service=+ep your-package-name then you will be able to listen on port 443/80 as a user.

More details about using setcap: https://wiki.apache.org/httpd/NonRootPortBinding