caddy: acme_server: error on reload

I started with this config:

{
  "apps": {
    "http": {
      "servers": {
        "srv0": {
          "listen": [
            ":80"
          ],
          "routes": [
            {
              "match": [
                {
                  "host": [
                    "localhost"
                  ]
                }
              ],
              "handle": [
                {
                  "handler": "acme_server"
                }
              ]
            }
          ]
        }
      }
    }
  }
}

To which I only added logging:

{
  "logging": {
    "logs": {
      "log0": {
        "writer": {
          "output": "stderr"
        },
        "encoder": {
          "format": "json"
        }
      }
    }
  },
  "apps": {
    "http": {
      "servers": {
        "srv0": {
          "logs": {
            "logger_names": {
              "localhost": "log0"
            }
          },
          "listen": [
            ":80"
          ],
          "routes": [
            {
              "match": [
                {
                  "host": [
                    "localhost"
                  ]
                }
              ],
              "handle": [
                {
                  "handler": "acme_server"
                }
              ]
            }
          ]
        }
      }
    }
  }
}

Ran caddy reload --config caddy.json and got the error:

ERROR	admin.api	request error	{"error": "loading config: loading new config: loading http app module: provision http: server srv0: setting up route handlers: route 0: loading handler modules: position 0: loading module 'acme_server': provision http.handlers.acme_server: initializing certificate authority: Error opening database of Type badger with source /Users/mohammed/Library/Application Support/Caddy/acme_server/db: error opening Badger database: Cannot acquire directory lock on \"/Users/mohammed/Library/Application Support/Caddy/acme_server/db\".  Another process is using this Badger database.: resource temporarily unavailable", "status_code": 400}

reload: sending configuration to instance: caddy responded with error: HTTP 400: {"error":"loading config: loading new config: loading http app module: provision http: server srv0: setting up route handlers: route 0: loading handler modules: position 0: loading module 'acme_server': provision http.handlers.acme_server: initializing certificate authority: Error opening database of Type badger with source /Users/mohammed/Library/Application Support/Caddy/acme_server/db: error opening Badger database: Cannot acquire directory lock on \"/Users/mohammed/Library/Application Support/Caddy/acme_server/db\".  Another process is using this Badger database.: resource temporarily unavailable"}

2020/11/13 21:22:08.725	INFO	admin	stopped previous server

Note the stopped previous server. I haven’t checked whether the acme endpoint still works.