collections.Index
每個索引項目必須是映射或切片：
{{ $s := slice "a" "b" "c" }}
{{ index $s 0 }} → a
{{ index $s 1 }} → b
{{ $m := dict "a" 100 "b" 200 }}
{{ index $m "b" }} → 200
使用兩個或更多鍵來訪問嵌套的值：
{{ $m := dict "a" 100 "b" 200 "c" (slice 10 20 30) }}
{{ index $m "c" 1 }} → 20
{{ $m := dict "a" 100 "b" 200 "c" (dict "d" 10 "e" 20) }}
{{ index $m "c" "e" }} → 20
您還可以使用鍵的切片來訪問嵌套的值：
{{ $m := dict "a" 100 "b" 200 "c" (dict "d" 10 "e" 20) }}
{{ $s := slice "c" "e" }}
{{ index $m $s }} → 20
使用 collections.Index 函數在鍵是變量時訪問嵌套的值。例如，這些是等效的：
{{ .Site.Params.foo }}
{{ $k := "foo" }}
{{ index .Site.Params $k }}