Error map
too many open files Go: accept tcp [::]:8080: accept4: too many open files / open x: too many open files
Go · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (11). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (11)
Error response from daemon: Pool overlaps with other one on this address space
Docker tried to create a network whose subnet clashes with an existing Docker network (or a VPN/host route).
driver failed programming external connectivity on endpoint: iptables: No chain/target/match by that name
Docker’s iptables rules were wiped (firewalld/ufw reload, iptables flush) while Docker was running, so it can’t publish ports.
Error response from daemon: network X not found
The container or Compose project refers to a Docker network that doesn’t exist (any more).
Go: cannot assign to struct field users["bob"].Age in map
Map values are not addressable, so you cannot modify a field of a struct stored directly in a map.
Go: cannot find package "github.com/pkg/errors" in any of: /usr/local/go/src/github.com/pkg/errors (from $GOROOT) /go/src/github.com/pkg/errors (from $GOPATH)
Go could not locate an imported package — it is not downloaded, the module is not initialised, or GOPATH mode is in effect.
Go: panic: assignment to entry in nil map
You wrote to a map that was declared but never initialised.
Go: listen tcp :8080: bind: address already in use
The port your Go server wants is already taken by another process (or a previous instance of your app).
Go: net/http: request canceled (Client.Timeout exceeded while awaiting headers)
An `http.Client` with a Timeout gave up waiting for the server's response headers.
Go: Get "https://api.example.com": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
An operation did not finish before its context deadline or HTTP client timeout.
Go: dial tcp 127.0.0.1:5432: connect: connection refused
Nothing is listening on the host and port your Go program tried to connect to.
Go: assignment mismatch: 1 variable but os.Open returns 2 values
The number of variables on the left does not match the number of values the function returns.
Two steps away (31)
docker compose: services.x Additional property y is not allowed / yaml: line N: mapping values are not allowed
The compose file is invalid YAML or uses a key Compose doesn’t recognise at that level (usually an indentation mistake).
docker-compose: command not found / 'compose' is not a docker command
Your system has only one of the two Compose flavours: the old docker-compose (v1) binary or the newer docker compose (v2) plugin.
service "web" depends on undefined service "db": invalid compose project
A service lists depends_on (or links/networks) for a service name that isn’t defined in the Compose file(s) being used.
Error: listen EADDRINUSE: address already in use :::3000
Another process is already listening on that port.
Docker: Bind for 0.0.0.0:80 failed: port is already allocated
Another container or host process already publishes that host port.
Cloudflare Error 1020: Access Denied
A Cloudflare firewall/WAF custom rule blocked the request — the visitor’s IP, country, user agent or request pattern matched a bl…
WARN: the attribute `version` is obsolete, it will be ignored
A harmless Compose v2 warning: the top-level version: line in docker-compose.yml is no longer used.
Docker container is unhealthy (health check failing)
The container is running, but its HEALTHCHECK command keeps failing, so Docker (and dependent services) consider it unhealthy.
spec.ports[0].nodePort: Invalid value: 80: provided port is not in the valid range. The range of valid ports is 30000-32767
A NodePort Service asked for a port outside the cluster’s NodePort range (default 30000–32767).
Go: ./main.go:5:2: "os" imported and not used
The file imports a package that no code in that file uses; Go treats this as a compile error, not a warning.
Go: ./main.go:12:2: undefined: handler
The compiler cannot find an identifier — a typo, a missing import, or it lives in another file/package that wasn't built.
Go: ./main.go:18:1: missing return
A function with a return type can reach its end without a return statement on some path.
Go: package app/models imports app/utils imports app/models: import cycle not allowed
Two or more packages import each other directly or indirectly, which Go forbids.
Go: x509: certificate signed by unknown authority
The Go TLS client does not trust the CA that signed the server's certificate.
Go: sql: no rows in result set
`QueryRow(...).Scan(...)` found no row for the query.
Go: panic: runtime error: invalid memory address or nil pointer dereference
The program used a pointer, map, interface or struct field that was nil — usually an uninitialised value or an ignored error.
Go: panic: runtime error: index out of range [3] with length 3
Code accessed a slice, array or string element beyond its length.
Go: panic: runtime error: slice bounds out of range [:5] with capacity 3
A slice expression `s[a:b]` used bounds outside the slice's length or capacity.
Go: panic: send on closed channel
A goroutine sent a value to a channel after it had been closed.
Go: panic: close of closed channel (or close of nil channel)
`close(ch)` was called twice, or on a nil channel.
Go: panic: sync: negative WaitGroup counter
`wg.Done()` was called more times than `wg.Add()`.
Go: http: superfluous response.WriteHeader call from main.handler (main.go:25)
A handler wrote the status header more than once, or wrote the body first (which sends 200) and then tried to set another status.
Go: context canceled (rpc error: code = Canceled desc = context canceled)
The context was cancelled before the operation finished — the caller gave up, the client disconnected, or a parent was cancelled.
Go: panic: test timed out after 10m0s — running tests: TestFoo (10m0s)
`go test` killed the test binary because it exceeded the timeout (default 10 minutes), usually a hung test.
Google API: 429 RESOURCE_EXHAUSTED — Quota exceeded for quota metric 'Read requests' and limit 'Read requests per minute per user'
Your project or user exceeded an API rate or daily quota.
Go: invalid character '<' looking for beginning of value
The decoder received something that is not JSON — often an HTML error page, an empty body or plain text.
Go: x509: certificate is valid for www.example.com, not api.example.com
The server's certificate does not list the hostname you connected to (SAN mismatch), or it has expired.
Go: sql: database is closed
The `*sql.DB` handle was closed (or the connection died) before the query ran.
Go: ./main.go:9:6: no new variables on left side of :=
`:=` declares variables, but all names on the left already exist in the same scope.
Go: invalid operation: a + b (mismatched types int and float64)
You combined two values of different types; Go never converts numeric types implicitly.
Go: cannot use "5" (untyped string constant) as int value in argument to f
A value's type is not assignable to the type required by the variable, parameter or return value.
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