Add solution for yr-channels-bug

yr-channels-bug/Makefile

@@ -0,0 +1,34 @@
+APP=algo/yr-channels-bug
+.PHONY: help
+help: Makefile ## Show this help
+	@echo
+	@echo "Choose a command run in "$(APP)":"
+	@echo
+	@fgrep -h "##" $(MAKEFILE_LIST) | sed -e 's/\(\:.*\#\#\)/\:\ /' | fgrep -v fgrep | sed -e 's/\\$$//' | sed -e 's/##//'
+
+.PHONY: build
+build: ## Build an application
+	@echo "Building ${APP} ..."
+	mkdir -p build
+	go build -o build/${APP} main.go
+
+run: ## Run an application
+	@echo "Starting ${APP} ..."
+	go run main.go
+
+test: ## Run an application
+	@echo "Testing ${APP} ..."
+	go test
+
+bench: ## Run an application
+	@echo "Benchmarking ${APP} ..."
+	go test -bench=. .
+
+clean: ## Clean a garbage
+	@echo "Cleaning"
+	go clean
+	rm -rf build
+
+lint: ## Check a code by golangci-lint
+	@echo "Linter checking..."
+	golangci-lint run -c golangci.yml ./...

yr-channels-bug/README.md

@@ -0,0 +1,65 @@
+# Yuri Romanov
+From chat
+
+Есть код, нужно найти ошибку и исправить:
+
+```Go
+package main
+
+import (
+"fmt"
+)
+
+func main() {
+work := []int{1, 2, 3, 4, 5, 6, 7, 8}
+in := generateWork(work)
+
+	out1 := fanOut(in)
+	out2 := fanOut(in)
+	out3 := fanOut(in)
+	out4 := fanOut(in)
+
+	for range work {
+		select {
+		case value := <-out1:
+			fmt.Println("Output 1 got:", value)
+		case value := <-out2:
+			fmt.Println("Output 2 got:", value)
+		case value := <-out3:
+			fmt.Println("Output 3 got:", value)
+		case value := <-out4:
+			fmt.Println("Output 4 got:", value)
+		}
+	}
+
+}
+
+func fanOut(in <-chan int) <-chan int {
+out := make(chan int)
+
+	go func() {
+		defer close(out)
+
+		for data := range in {
+			out <- data
+		}
+	}()
+
+	return out
+}
+
+func generateWork(work []int) <-chan int {
+ch := make(chan int)
+
+	go func() {
+		defer close(ch)
+
+		for _, w := range work {
+			ch <- w
+		}
+		return
+	}()
+
+	return ch
+}
+```

yr-channels-bug/go.mod

@@ -0,0 +1,3 @@
+module github.com/skosovsky/algo/yr-channels-bug
+
+go 1.21.5

yr-channels-bug/golangci.yml

@@ -0,0 +1,160 @@
+linters-settings:
+  depguard:
+    # new configuration
+    rules:
+      logger:
+        deny:
+          # logging is allowed only by logutils.Log,
+          # logrus is allowed to use only in logutils package.
+          - pkg: "github.com/sirupsen/logrus"
+            desc: logging is allowed only by logutils.Log
+  dupl:
+    threshold: 100
+  funlen:
+    lines: -1 # the number of lines (code + empty lines) is not a right metric and leads to code without empty line or one-liner.
+    statements: 50
+  goconst:
+    min-len: 2
+    min-occurrences: 3
+  gocritic:
+    enabled-tags:
+      - diagnostic
+      - experimental
+      - opinionated
+      - performance
+      - style
+    disabled-checks:
+      - dupImport # https://github.com/go-critic/go-critic/issues/845
+      - ifElseChain
+      - octalLiteral
+      - whyNoLint
+  gocyclo:
+    min-complexity: 15
+  gofmt:
+    rewrite-rules:
+      - pattern: 'interface{}'
+        replacement: 'any'
+  goimports:
+    local-prefixes: github.com/golangci/golangci-lint
+  gomnd:
+    # don't include the "operation" and "assign"
+    checks:
+      - argument
+      - case
+      - condition
+      - return
+    ignored-numbers:
+      - '0'
+      - '1'
+      - '2'
+      - '3'
+    ignored-functions:
+      - strings.SplitN
+
+  govet:
+    check-shadowing: true
+    settings:
+      printf:
+        funcs:
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Infof
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Warnf
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Errorf
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Fatalf
+  lll:
+    line-length: 140
+  misspell:
+    locale: US
+  nolintlint:
+    allow-unused: false # report any unused nolint directives
+    require-explanation: false # don't require an explanation for nolint directives
+    require-specific: false # don't require nolint directives to be specific about which linter is being skipped
+  revive:
+    rules:
+      - name: unexported-return
+        disabled: true
+      - name: unused-parameter
+
+linters:
+  disable-all: true
+  enable:
+    - bodyclose
+    - depguard
+    - dogsled
+    - dupl
+    - errcheck
+    - exportloopref
+    - funlen
+    - gocheckcompilerdirectives
+    - gochecknoinits
+    - goconst
+    - gocritic
+    - gocyclo
+    - gofmt
+    - goimports
+    - gomnd
+    - goprintffuncname
+    - gosec
+    - gosimple
+    - govet
+    - ineffassign
+    - lll
+    - misspell
+    - nakedret
+    - noctx
+    - nolintlint
+    - revive
+    - staticcheck
+    - stylecheck
+    - typecheck
+    - unconvert
+    - unparam
+    - unused
+    - whitespace
+
+  # don't enable:
+  # - asciicheck
+  # - scopelint
+  # - gochecknoglobals
+  # - gocognit
+  # - godot
+  # - godox
+  # - goerr113
+  # - interfacer
+  # - maligned
+  # - nestif
+  # - prealloc
+  # - testpackage
+  # - wsl
+
+issues:
+  # Excluding configuration per-path, per-linter, per-text and per-source
+  exclude-rules:
+    - path: _test\.go
+      linters:
+        - gomnd
+
+    - path: pkg/golinters/errcheck.go
+      text: "SA1019: errCfg.Exclude is deprecated: use ExcludeFunctions instead"
+    - path: pkg/commands/run.go
+      text: "SA1019: lsc.Errcheck.Exclude is deprecated: use ExcludeFunctions instead"
+    - path: pkg/commands/run.go
+      text: "SA1019: e.cfg.Run.Deadline is deprecated: Deadline exists for historical compatibility and should not be used."
+
+    - path: pkg/golinters/gofumpt.go
+      text: "SA1019: settings.LangVersion is deprecated: use the global `run.go` instead."
+    - path: pkg/golinters/staticcheck_common.go
+      text: "SA1019: settings.GoVersion is deprecated: use the global `run.go` instead."
+    - path: pkg/lint/lintersdb/manager.go
+      text: "SA1019: (.+).(GoVersion|LangVersion) is deprecated: use the global `run.go` instead."
+    - path: pkg/golinters/unused.go
+      text: "rangeValCopy: each iteration copies 160 bytes \\(consider pointers or indexing\\)"
+    - path: test/(fix|linters)_test.go
+      text: "string `gocritic.go` has 3 occurrences, make it a constant"
+
+run:
+  timeout: 5m
+  skip-dirs:
+    - test/testdata_etc # test files
+    - internal/cache # extracted from Go code
+    - internal/renameio # extracted from Go code
+    - internal/robustio # extracted from Go code

yr-channels-bug/main.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	work := []int{1, 2, 3, 4, 5, 6, 7, 8}
+	in := generateWork(work)
+
+	out1 := fanOut(in)
+	out2 := fanOut(in)
+	out3 := fanOut(in)
+	out4 := fanOut(in)
+
+	// Simple
+	for i := 0; i < len(work); {
+		select {
+		case value, ok := <-out1:
+			if ok {
+				i++
+				fmt.Println("Output 1 got:", value)
+			}
+
+		case value, ok := <-out2:
+			if ok {
+				i++
+				fmt.Println("Output 2 got:", value)
+			}
+
+		case value, ok := <-out3:
+			if ok {
+				i++
+				fmt.Println("Output 3 got:", value)
+			}
+
+		case value, ok := <-out4:
+			if ok {
+				i++
+				fmt.Println("Output 4 got:", value)
+			}
+
+		}
+	}
+
+	// Spinlock - более оптимальный варианты, т.к. nil каналы не проверяет select
+	for i := 0; i < len(work); i++ {
+		select {
+		case value, ok := <-out1:
+			if !ok {
+				i--
+				out1 = nil
+				continue
+			}
+			fmt.Println("Output 1 got:", value)
+		case value, ok := <-out2:
+			if !ok {
+				i--
+				out2 = nil
+				continue
+			}
+			fmt.Println("Output 2 got:", value)
+		case value, ok := <-out3:
+			if !ok {
+				i--
+				out3 = nil
+				continue
+			}
+			fmt.Println("Output 3 got:", value)
+		case value, ok := <-out4:
+			if !ok {
+				i--
+				out4 = nil
+				continue
+			}
+			fmt.Println("Output 4 got:", value)
+		}
+	}
+}
+
+func fanOut(in <-chan int) <-chan int {
+	out := make(chan int)
+
+	go func() {
+		defer close(out)
+
+		for data := range in {
+			out <- data
+		}
+	}()
+
+	return out
+}
+
+func generateWork(work []int) <-chan int {
+	ch := make(chan int)
+
+	go func() {
+		defer close(ch)
+
+		for _, w := range work {
+			ch <- w
+		}
+		return
+	}()
+
+	return ch
+}